EVALUATION OF RECORDING TECHNIQUES

• Document Type: CREST
• Collection: General CIA Records
• Document Number (FOIA) /ESDN (CREST): CIA-RDP78-03300A001600040005-4
• Release Decision: RIPPUB
• Original Classification: K
• Document Page Count: 55
• Document Creation Date: December 22, 2016
• Document Release Date: January 3, 2012
• Sequence Number: 5
• Publication Date: June 1, 1955
• Content Type: REPORT

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EVALUATION OF RECORDING TECHNIQUES
June 1, 1955
STAT
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Physics Department
Prepared by
Chairman, ysics Department
June 1, 1955
Copy No. 1 of 3 Copies
STAT
STAT
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II. Definitions of Terms
III. Criteria for Recording System Evaluation
IV. Basic Types of Recorders
V. Data Sheets for Recording Systems
VI. Critical Evaluation
VII. Bibliography
Appendix A Energy Conversion Processes and Recording
Appendix B Communications Theory and Recording
Appendix C Mechanical Tolerances in Recording
Appendix D Record Geometry
Appendix E Recording Materials
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I. Introduction: The original statement of the task on which this work has
ase ca led for examination of the general possibilities of some ten
been 1- _d
recording techniques, primarily selected by examination of the Patent Office
files. Evaluation of resolution, dimensions and weight, availability, life,
operational practicality, ruggedness, power requirements, stability, and basic
limitations were desired.
Early in the work, it became evident that at least 100,000 different, realiz-
able recording systems could be synthesized by combinations of known principles
and by addition of new ideas. In view of this, it was essential to develop
bases for comparison of different systems, based on definitions of terms and
a system block diagram valid for the great majority of examples. This has
been done, within budget limitations.
Since recording of information is a fundamental and continuing problem, this
type of analytical effort is believed to be needed for comparison of possible
approaches to hardware development.
II. Definitions of Terms: Recording is essentially a communication process
wherein a message from a defined message source is received by the recording
apparatus or recorder concerned, =an is normally operated on in some manner
to derive a form of signal to be recorded. In this process, some noise is
unavoidably introduced. The signal plus noise are then applied to some kind
of recording medium or record as forms of energy inputs which cause a change
in state of the record, (and again in this process, noise may be introduced)
so that the record medium may finally be said to have stored or recorded the
signal (or the information represented by the signal).
At a later time, reading or reproducing apparatus can operate on the record
to recreate the signal with introduction of more noise, and the signal may
actuate a device which finally reproduces the message at the destination of
the particular sequence.
The entire process is shown in Fig. 1 in simplified block diagram form.
Nomenclature for the block labels has been carefully chosen; however the
diagram can be made more general by inclusion of feedback, and perhaps by
showing separate encoders for recording and scanning, as has been shown in
Fig. 2. Definitions of terms are given where necessary for this study as
follows. Terms not defined are encountered in recording literature, and
should be defined (along with many others) in a more comprehensive analysis.
Access Time: Longest time required to cause a specified element of a record
to be reproduced as a signal. Specification of a time usually implies scanning
of the record in some manner. Statistical definitions (e.g. mean access time)
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INFORMATION
SOURCE
SCANNING
SIGNAL
REC RDING
SIGNAL
SCANNER
POWER
SUPPLY
SCANNING
sm-
ENERGY
RECORDING
ENERGY
Figure I A RECORDING SYSTEM BLOCK DIAGRAM (SIMPLIFIED)
READER
POWER
SUPPLY
DECODER
POWER
SUPPLY
ENCODER
POWER
SUPPLY
NOISE
SISAL
RECORDING
POWER
SUPPLY
MESSSAGEJDESTINATION
Figure IB - READING SYSTEM BLOCK DIAGRAM (SIMPLIFIED)
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INFORMATION
SOURCE
y
SCANNING
ENCODER
POWER
SUPPLY
SCANNING
ENCODER
MARKING
ENCODER
MARKER
ENCODER
POWER
SUPPLY
SCANNING
ENERGY
POWER
SUPPLY
RECORDER
(SCANNER)
RECORDER
(MARKER)
RECORDING
ENERGY
POWER
SUPPLY
Figure 2 - RECORDER BLOCK DIAGRAM (FEEDBACK ELEMENTS NOT SHOWN).
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can be established, their nature depending on whether elements of information
are stored in an order representative of their frequency of use, or in
other orders.
Analog Data: Information expressed by specifying the amplitude of a signal
for eachinstant of time during the duration of a message.
Binary System:
Bit: A basic unit of measure of information. One bit represents the infor-
mation which can be stored by a device with two stable states.
Code: A code is a system for operating on a message (or a signal) in such
a way as to produce signals suitable for recording by a particular process.
Coder: (See Encoder).
Coding: (See Encoding).
Coding System: (See Encoder or Code)
Data: (See Information).
Data Presentation: The process of making a message available to its destina-
tion in suitable form.
Data Reduction: The process of operating on stored information to increase
its usefulness for a particular purpose.
Data Representation:
Decoder: A device which operates on a coded signal in a predetermined manner
so as to produce a message corresponding to the signal.
Decoding: The process of operating on a coded signal in such a manner as to
prima message suitable for use by the destination of the message.
Decoding System: (See Decoder).
Destination: A device or system capable of receiving a message.
Digital Data:
Encoder: A device which operates on a message in such a manner as to suit the
ink ation contained in the message to transmission as a signal, i.e., a
device which operates on a message and produces a signal.
Encoding: The process of operating on a message to produce a signal represent-
ingthhemessage.
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Energy Dimensions:
Head: (See Stylus).
Information: Knowledge describing the present or past operation of one or
more physical systems.
Information Capacity: (See Information Storage Capacity).
Information Gain: Reduction in uncertainty or ignorance due to reception of
information.
Information Source: A device or system which produces or generates a message
conveying orma ion.
Information Storage: A process whereby the knowledge of events may be
perpetuated.
Information Storage Capacity: The property of a-record measured by the number
of stable states which can be distinguished in the record by the proper read-
ing devices.
Information Storage Density:
Information Theory: Theory which establishes measures of information storage
capacity, inform a ion content of messages, and related parameters. The theory
also relates the rate at which information can be operated on by a system to
bandwidth, power, accuracy, coding, etc.
Logging: (See Recording).
Mark: An element of a recording, not necessarily visible. This may be taken
as the physical evidence that recording energy has been applied to the record
medium at a specified point.
Memory: (See Record).
Memory Device: (See Record).
Memory Transfer Function:
Message: The output of an information source, usually one or more time
functions representing information.
Modulation:
Noise: Energy introduced into the recording or reading process which causes
the message reaching the destination to contain undesired differences from
the original message fed into the system.
Noise Figure:
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Pickup: (See Stylus).
Playback:
Quantization:
Radix:
Reader: A device which operates on a record and produces a signal corres-
ponTi-ng to the recorded information. This is usually done by directing
scanning energy and reading energy to the record or recording medium.
Reading Accuracy:
Reading Aperture:
Reading Energy: Energy applied to the record medium to convert the change
of state corresponding to a mark into a signal element. The mark may, or
may not, be altered by the reading energy.
Reading Precision:
Reading Resolution:
Reading Speed:
Record: A physical system which can undergo a relatively permanent change
in state when operated on by (energy from) a recorder.
Record Capacity:
Recorder: A device which accepts a signal and operates on a recording medium
in a manner so as to change the physical state of the medium to represent the
signal, such that when the recording medium is subsequently explored by a
reader the signal can be recreated. Usually the recorder serves to modulate
streams of energy directed toward the recording medium, including scanning
energy and recording energy.
Recording: Perpetuation of knowledge by transforming a recording medium so
that when operated on by a reader or reproducer the medium will perform the
act of reproducing that knowledge.
Recording Accuracy:
Recording Aperture:
Recording Energy: Energy which causes a change in state of an element of a
recor medium when applied to that element. The energy is controllable by
the signal to be recorded in some manner.
Recording Medium: (See Record).
Recording Precision:
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Recording Resolution: A measure of the smallest element of area (or volume)
of the record which can store one or more bits of information. May be speci-
fied in bits per square inch, bits per cubic inch, or some other form such as
lines per inch, etc.
Recording Speed:
Recording Stylus: (See Stylus).
Recording System: A system which performs the act of recording. The term
often implies inclusion of a reading or reproducing system.
Reproducer: (See Reader).
Reproducing Stylus:
Sampling:
Scanning: A process by which a record is explored in a predetermined manner.
Positioning of the record may be involved.
Scanning Aperture:
Scanning Energy: Energy employed to cause a recording medium to be systematically
scanned or explored by a stream of energy in order to record or reproduce signal
elements.
Self-Checking Code:
Signal: A stream of time-varying energy representing information encoded in
some manner.
Signal/Noise Ratio:
Space Dimensions:
Space Domain Systems:
Stable State: A condition of an element of a record which can be distinguished
row m other states by the reader.
Stable State Levels:
Storage Density: (See Information Storage Density).
Store: (See Record).
Stylus: A device by which recording or reading energy is applied to (or
withdrawn from) a record. Although this term is normally applied only to
mechanical systems, it will be preferred to other terms such as t'Head" for
simplicity.
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Al pickup needle or holder furnished with a jewel or other abrasive-resistant
tip. A stylus may or may not be arranged for convenient replacement.
Time Dimension:
Time Domain Systems:
Transfer Function:
Weighing:
Writing: (See Recording).
III. Criteria for Evaluation of Recording Systems: The reason for comparative
evaluation of recording systems is usually a specific operating need which
must be filled as well and as quickly as possible. On the other hand, exist-
ing production equipment may fall so far short of meeting performance demands
that the question in some cases becomes one of choosing a fundamental princi-
ple judged most suitable for development toward the ultimate goal.
In the first case, specifications may be kept quite simple. In the latter
instance, a great deal more must be knovTn about systems. Thus, it seems
appropriate to establish a few simple recording system requirements, and then
to examine the most general comparison criteria possible.
Elementary Criteria: There are a few factors which must be specified for any
recording system. In a rough order of operating importance for the typical
"practical" case, these are given in Table I for the most popular type of
current system - magnetic tape - based on manufacturers' literature. Similar
factors may be compiled for other systems, and generalized to form a basis for
comparison. The first ten factors seem to be of greatest interest.
These practical factors can be analyzed in many ways, although the ambiguity
of terms commonly used in manufacturers' literature makes the process
difficult. Some "recording systems" or recorders include playback or reading
facilities. Others do not. If the factors of Table I are separated into
classes, one might use the data sheet of Fig. 3. Due to the limited scope
of the present study, an even simpler data sheet was actually used.
Basic Criteria: In the line of basic criteria, it is of interest to note that
Gerhard Hol ander2 selected the factors of resolution; minimum practical spot
area; maximum practical density (bits per cubic inch); operating speed for
recording and reading; cost per bit; and number of physical states possible
TIRE Standards on Electroacoustics: ')efinitions of Terms, 1951.
2Gerhard Hollander, "Digital Data Recorder. An Investigation of Dense Storage
of Information" M.I.T. Servo Lab Tech. Memo. No. 6897-TM-12, October, 1953
IkSTIA AD No. 21487).
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Specification
1. Recording Time
2. Frequency Response
3. Size
4. Weight
5. Power Consumption
6. Type of Power Supply
7. Signal/Noise Ratio
8. Number of Input Channels
9. Input Channel Impedance(s)
10. Input Voltage Levels
(Hours)
(Range in Cycles/Second)
(Dimensions - Inches)
(Pounds)
(Watts)
(Voltage and Frequency)
(Decibels)
(Number)
(Ohms)
(vu)
11. Drive Motor Flutter (Per cent)
12. Record Speed(s) (Inches/Second)
13. Input Equalization Characteristic (Description)
14. Record Size Capacity (Reel Diameter - Inches)
15. Type of Drive Motor(s) (Description)
16. Type of Rewind Motor (Description)
17. Starting Time - Record (Seconds to Full Speed)
18. Stopping Distance - Record (Distance Record Moves - Inches)
19. Provision for Monitoring (Description)
20. Output Impedance(s) (Ohms)
21. Output Power (Watts)
22. Output Voltage(s) (Volts)
23. Type of Recording Head (Description)
2I. Provision for Controls (Type and Number)
25. Playback Time Accuracy (Seconds/Minute of Recording)
26. Record Loading Features (Description)
27. Rewind Time (Seconds)
Table I
Practical System Specifications - Magnetic Tape Recorders
(Magnecord Models M30 and M80. Ampex Models 350 and 600)
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Recording and Reading System Data Sheet Type of Process
Description of System:
Availability:
Recording System
Frequency Response Range (Cycles/Second)
Power Consumption (Watts) Type Power Supply
Signal/Noise Ratio Input Impedance (Ohms)
Input Voltage Range (Volts) No. Channels
Record Drive Noise Type Drive
Input Equalization
Record Size Capacity Record Starting Time (Seconds)
Record Stopping Distance or Time
Provision for Monitoring
Controls
Type Recording Head
Recording Time (Seconds) Signal/Noise Ratio
No. of Channels Scanning Speed
Record Storage Capacity (Bits)
Scanning Geometry
Reading System
Frequency Response Range (Cycles/Second)
Power Consumption (Watts) Type Power Supply
Signal/Noise Ratio Type Drive
Reading Drive Noise Output Power (Watts)
Output Impedance (Ohms)
General
Weight (Lbs.) Dimensions (Inches)
Fig. 3 - Proposed Data Sheet
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for one element of area. His problem apparently did not require power or
energy considerations, but usually energy, accuracy, space, and rate of
storage considerations can be ""bartered"' - one for the other - in a manner
similar to power, bandwidth, reliability, and rate of data transmission in a
communications system. Therefore energy must be taken into account. Indeed
as this study has proceeded it has become increasingly evident that the supply,
handling, and storage of energy are the main avenues along which further
effort must be directed. (See Appendix A.)
To establish the more detailed considerations useful for prediction of ultimate
capabilities of systems, it is useful to use the diagram of Fig. 1 as a basis,
since choice of a system may finally depend on factors such as adaptability
to coding, noise figure, ruggedness, or the like. Evidently, if one can
specify the performance of each system element independently, it might be
possible to synthesize an optimum recorder from operating requirements.
Because of interactions among elements, the problem is not this simple. The
"optimum" coder may be unsuited for use with the "optimum" scanning system,
etc. However the building block approach is the most systematic, and so is
followed here.
Detailed specifications must be worked out for each block in the diagram of
Fig. 1. The blocks should be chosen so that they are as independent as
possible, so that the most combinations of any group of blocks can be made.
Encoder Evaluation: The function of the encoder must not be minimized in
importance. It receives a message of input information from outside the
recording system (consisting of the output of a radio receiver, the voltage
from an electrical transducer, or the like) and operates on this information
to produce a signal suitable for recording.
Sometimes the encoder may only serve to make the recording process more effi-
cient, such as by sampling the input information at intervals. At other times,
the recording process cannot function without encoding. For example, the
Ampex Model 700 recorder must modulate a carrier with low frequency geophysical
data which cannot be recorded directly on magnetic tape.
Sanpling is an extremely valuable function, since it can remove a burden
of useless data from the recorder elements. In most recording, far more
information is placed on the record than ever can or need be evaluated on
playback. An example of useful coding is the actuation of the record drive
only when a predetermined change takes place in the quantity being recorded.
Encoders can involve analog to digital data translation or conversion, genera-
tion of timing or marking signals, conversion of DC power to AC for synchronous
motor drive, modulation, and many other processes. In the block diagram of
Fig. 1, a single box is shown with both scanning and recording signal outputs
to the recorder element. It is necessary to show both outputs because the
two signals are often related in some manner.
There is justification for showing separate boxes for scanning and recording
encoders as in Fig. 2. Consider a disc recorder which does not space grooves
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arbitrarily, but which (at a low frequency) positions the stylus for one
groove by moving it as close as possible to the previous groove. This is a
scanning coding operation, dependent primarily on the amplitude of previous
signals (and the corresponding width of the lateral cut).
Information needed on encoders for evaluation includes the following:
1.
Forms of Messages Accepted
a.
Input Voltage Range
Dynamic Range)
b.
c.
d.
Input Impedance
No. of Input Channels
Input Frequency Range
e.
Input Modulation (AM, FM, or PM)
f.
Coding of Input Signals
g.
Type of Energy Input
2. Forms of Outputs to Recorder
a. Types of Coding Applied to Message
b. No. of Output Channels
c. Output Powers
d. Output Impedances
NOTE: This assumes electrical messages. Others should be added for
mechanical and other messages.
3. Overall Coder Performance
a. Frequency Response
b. Noise Figure
c. Amplitude and Phase Distortion
d. Coder Power Efficiency (Watts/Bit)
e. Stability
4. Physical Characteristics
a. Dimensions
b. Weight
c. Ambient Temperature Range
d. Ambient Humidity Range
e. Ruggedness
f. Power Supply Requirements
Recorder Evaluation: This element is defined as the part of the system
which actually operates on the record to produce changes in state. For
example, a disc recording system would place in this category only the drive
motor, turntable, and the magnetic or other cutting head. The lead screw
mechanism could be considered as part of the drive motor since its guidance
of the cutting head is unrelated to the signal or its coding. Scanning
energy output would consist of the energy moving the cutting head in its
spiral track along the disc, while recording energy would be that actuating
the cutter. This distinction is not simple or obvious, since the pressure
of the cutting head against the record forces the drive motor to supply part
of the cutting energy.
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Information required for evaluation of recorder elements includes:
1.
Forms of Signals Accepted
a.
b.
c.
d.
e.
f.
No. of Input Channels
Input Impedance
Input Power Range
Input Frequency Range
Forms of Input Coding
Types of Energy Input
2.
Forms of Recording Energy Outputs to Record
a.
b.
c.
d.
e.
No. of Output Channels
Form of Recording Energy
Output Power Range
Output Impedances
Recording Energy Frequency Range
3.
Forms of Scanning Energy Outputs to Record
a. No, of Output Channels
b. Form of Scanning Energy
c. Output Powers
d. Output Impedances
e. Scanning Energy Frequency Range
Overall Recorder Performance
a.
b.
Total Running Time
Record Starting Time
(or Distance)
c.
Record Stopping Time
(or Distance)
d.
e.
Scanner Noise Figure
Recorder Noise Figure
f.
Type of Operation Performed on Record
g.
Power Efficiency
5. Physical Characteristics
a. Power Supply Requirements
b. Dimensions
c. Weight
d. Ambient Temperature Range
e. Ambient Humidity Range
f. Ruggedness
Record (Recording Medium) Evaluation: Since the effort of the entire writing
system is to change the state of elements of the record, properties of these
components are essential to evaluation. Information required includes:
1. Type of Change in State
a. Mechanism of Energy Storage
b. Energy Conversion Processes Involved
c. Energy Units of Change of State Measurement
d. Density of Stored Energy
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2. Energy Requirements - Recording
a. Forms of Energy Accepted
b. Range of Energy Input Rate
c. Stored Energy per Bit of Stored Information
3. Energy Requirements - Scanning
a. Forms of Energy Accepted
b. Range of Scanning Energy Input Rate
c. Energy Required per Unit of Scanning
d. Possible Types of Scanning Geometry
1.. Record Performance
a. Time Stability
b. Human Convenience of Record Data Presentation
c. Access Requirements
d. Processing Requirements
e. Noise Figure
f. Harmonic Distortion
g. Record Frequency Response
5. Physical Characteristics
a. Color(s)
b. Dimensions
c. Weight
d. Ruggedness
e. Temperature Coefficient of Stability
f. Humidity Coefficient of Stability
g. Power Supply Requirements
Reading System Evaluation: Similar criteria can be set up for each element
of a ea ding system. Since a reading system which can get the most out of
a record is almost a part of the recording system, this should be done.
Reading systems were not considered specifically in definition of the original
tasks on this project.
Overall System Evaluation: Since all records are intended to be subjected
to later reading, complete recording - reading systems must be analyzed.
There are a number of unique factors such as the ratio of complexity of the
reader to that of the recorder which must be developed.
IV. Basic Types of Recording Systems: With some criteria established for
evaluating (if not for measuring) recording system performance, it is possible
to consider the number of possible systems which can be compared.
Commercially available systems unfortunately offer a very poor index of basic
system promise. A system based on physical principles which are fundamentally
inferior may reach a high state of engineering development (and consequently
lower cost and wide acceptance) due to the energy and persistence of its
proponents. Magnetic tape recording - evidently a promising principle - was
only developed through a random process requiring many years. If the overall
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problem is systematically to apply effort to the areas which are the most
promising from a scientific standpoint, all physically realizable systems
should be listed, and elimination of all but a few should be made in an
organized manner.
Since recording is broadly defined as the application of energy to a material
in such a way as to produce a reasonably permanent change in state, energy
is a primary consideration. Appendix A indicates useful work which can be
done in treating recording and reading as energy conversion processes.
Study of the many possible methods of organizing the classification of all
possible recording systems has suggested the following categories, which are
presented in outline form because each can be applied separately to a system.
Possible Types of Recording Systems
I. Recording System Function: All recording systems must function as parts
of playback systems (where the record marking is not necessarily visible,
but playback is the main function), as graphic systems (where the primary
function is to provide a visible record), or as combination systems (where both
playback and visibility requirements are fulfilled). Examples of these systems
in order are magnetic wire, ordinary recording pen on chart, and boundary
displacement systems. (3)
A. Types of Energy Input: Recording systems of any of the above types
may accept info amion inputs of different energy forms. The input energy form
is commonly an electrical voltage or a mechanical displacement, or can be
converted to one of ese y sul able transducers not consi ered normally as
a part of the recorder. An example of an electrical voltage input is the
output of a photomultiplier tube, while a recording accelerometer with a
pen scratching smoked glass, actuated by the displacement of a mass against
a spring system is an example of a mechanical displacement input. (2)
1. Form of Energy Input: Any of the above systems may receive energy
in analog or digital form, or conceivably a combination of both, since a chain
of code - modulated pulses could be amplitude - modulated y a separate source
of information. The number of separate channels which can be handled, and
the input bandwidth, are affected by this category. (3)
a. Form of Recorder Coding: Any of the 3 x 2 x 3 systems outlined
above may require further coding by the recorder to achieve optimum results
for a given system. For these urposes coding is defined broadly to include
such operations as modulating a carrier with the incoming signal, as is
necessary to record very low frequency analog data on magnetic tape. Although
many types of coding can be conceived, six would seem to suffice for most
purposes, including coding either related or independent of the manner in which
the record is scanned, and in each of these categories, the alternatives of an
amplitude, frequency, or pulse modulated output. (6)
(1) Type of Applied Recording Energy: Systems of the above
types may actually app y at least different es of energy to an element
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of area of a record. Although obviously a matter of definition, these have
been chosen after review of the collected list of subject headings in
Physics Abstracts as:
A.
Mechanical
F.
Magnetic
B.
Acoustic
G.
Electronic
C.
Optical
H.
Electromagnetic
D.
Thermal
I.
Nuclear
E.
Electrical
J.
Chemical
These are used as the principal basis for classifying all possible systems
because additional categories will need to be added only if new forms of
energy are discovered or adopted in general usage. (10)
(a) Change of State Produced in Record: Obviously, the
same type of recording energy applied to different ma er s can cause dif-
ferent types of effects on the record, depending on the nature of the latter.
For example, the application of heat to records could be made to result in
color changes, deformation of the record material, changes in degree of
magnetization, etc. Considering changes of the same nature (e.g. color
changes) but in different materials (e.g. paper, metal foil, wax, or plastics)
as separate types, it is estimated that a single type of applied recording
energy can cause at least 12 different types of changes of state, on the
average. (12)
((l)) Form of Scanner Coding: Scanning can be coded
in a manner completely independent of all of the previous variables. In
fact, a recorder with digital chart drive (from an escapement mechanism) and
analog stylus drive (using a conventional DtArsonval pen movement) can be
easily visualized. This would seem to allow multiplication of the number of
possible systems by at least the factor of 3, for the three common types of
modulation. (3)
((a)) Type of Applied Scanning Ener : If this
energy is considered as furnishing "chart" drive, there are ten possible forms
of energy, as in (1) above. Actually, this term can broadly be interpreted
to include the specification of both stylus and chart drive, so that many
more combinations seem realistic. (10)
Even on this basis, which can probably be expanded by further study, the
number of separately identifiable recording systems might be as high as
3 x 2 x 3 x 6 x 10 x 12 x 3 x 10, or 388,000. To show that each separate
specification is necessary, the hypothetical example of a package shock
recorder used:
I. Recording System Function: Should be combination system, with
record visib le or easy monitoring., but capable of automatic statist cal
analysis of a large number of records.
A. Type of Energy Input: Will be mechanical displacement, since
the data to be recorded measures the shocks experienced by a package of
material in transit over a period of weeks or months.
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1. Form of Energy Input: Will be analog, since it is desired
to know the amplitude of each shock as a function of its duration.
a. Form of Recorder Coding: Will be amplitude modulation
of a mechanical signal, since an accelerated mass will drive a recording
stylus perpendicular to the direction of chart travel. Acceleration is
converted to displacement by a spring-loaded mass.
(1) Type of Ap lied Recording Energy: Will be mechani-
cal - motion of spring-loaded stylus across record material.
(a) Change of State Produced in Record: Material
removal - scratching of stylus across smoked glass plate.
((1)) Form of Scanner Coding: Since chart
must be moved at one constant speed while no shocks are being experienced
and at another (faster) constant speed during shocks, pulse modulation of the
independent (scanning) variable is required. Geometry is linear x -y system
since stylus moves in straight line.
((a)) Type of Scanning Energy: Clock-
work motor will be used, with two speeds selectable by a sensitive threshold
accelerometer independent of that used for stylus motion. Thus scanning energy
is mechanical.
V. Data Sheets for Recording Systems: On the basis of the actual forms of
energy applied to change the state of an element of record area (or volume),
there are ten possible categories. Sample rough data sheets for recorders
in some of these categories are shown to the limited extent possible in this
brief study. The design of the data sheet is subject to improvement by
further work on Chapter III of this report. It is believed that at least
1000 data sheets could be included in a reasonably thorough coverage of
systems worth evaluation on separate bases. At the beginning of each section
is a tabulation of the various principal types of subclasses conceived for
each system to date.
Combination Systems: Some systems combine one or more forms of recording
energy, for example, when a blast of heated gas is directed at a record.
Such systems should be classified under both energy headings when the change
in state of the record results partially from each type of energy.
Conclusions: It is not possible to compute such important factors as
recor storage capacity or storage density from the typical manufacturers
information. Noise figures are seldom given, nor are power supply require-
ments of the recording process itself isolated.
A. Mechanical Recording Energy Systems: In these systems mechanical
energy is applied to the recording material, and actually causes the change
in state of the record material. (The strict definition of the term,
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ttchange in state, tt must be liberalized to include mechanical transfer of
materials such as ink to the recording medium.) Principal types of these
systems are:
1.
Material Removed From Record
a.
b.
c.
d.
e.
Punched Holes or Voids (Punch)
Notched Edges (Punch)
Scratched Grooves (Stylus)
Cut Grooves (Stylus)
Absorption of Gas or Liquid from Record
2.
Material Added to Record
a. Ink (Pen)
(1) Magnetic Ink
(2) Dye - Containing Ink
(3) Radioactive Ink
b. Pencil
(1) Graphite Pencil
(2) Fluid Graphite Pencil
(3) Radioactive Pencil
(Li) Magnetic Particle Pencil
c.
Liquid Spray
(1) Magnetic Liquid
(2)
Dye-Bearing Liquid
(3)
Radioactive Liquid
d.
Gas
Spray
e.
Sputtered Wax
f.
Spray of Solid Particles (Aerosols)
3. Record Material Displaced
a. Embossing Stylus
b. Gas Jet Stream
c. Abrasive Particle Stream
1.. Record Material Changed in Physical State
a. Contact Stylus - Pressure Sens- ive Record
General Criteria - Mechanical Systems
a. Ungrooved or Pregrooved Blanks
b. Stylus Motion - Vertical or Lateral
c. Stylus Drive
(1) Electromagnetic
(2) Electrostatic
(3) Piezoelectric
(L) Hydraulic
(5) Mechanical
d. Records Processed or Unprocessed after Recording
e. Record Materials - Rheology
f. Gas or Liquid Propulsion Means
(1) By Pump
(a) Form of Actuating Energy
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(2) By Capillary Action
(3) By Gas Pressure
(4) By Gravity
g. Number of Possible States of Record Element of Area
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Type
Recording Process
Description of Process Ink-Paper
(Brush Penmotor)
Mechanical
Geometry- Paper Chart Pen Length 3 in.; 140 mm peak to peak pen swing
up to 70 CPS
Time Duration Range ---
Frequency Response 0.2 to 100 CPS (With amplifier) for 80% of maximum
0 to 30 CPS No amplifier) for 100% of maximum
Total Record Storage Capacity
Dimensions of Recorder 5' x 4" x 1-5/8" Pen Overhang 1-3/811
Input 1500 ohms
Weight 4 lbs.
Power Supply
Reproducer
Driving Impedance for Optimum Damping 250 ohms
Sensitivity 1.1 mm./volt or 1.6 mm/ma at pen point
Anti-Freeze Ink Purple, suitable to -20? F.
Pen Friction Signals giving less than 2 mm deflection may be affected.
Storage Density Not known, since width of pen trace not specified
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Type
Recording Process
Mechanica
Description of Process Embossing - Film
(Miles Reproducer Co. "Walkie Recordall")
Geometry Belt - 150 hours can be filed in container 1" x 3" x 6"
Time Duration Range 90 minutes to 8 hours (Lt hours per side)
Frequency Response Not specified - probably to 2500 cycles
Total Record Storage Capacity
Dimensions of Recorder 14" x 9" x 15"
Input
Weight U.S lbs. for model CC1B
Power Supply Flashlight cells plus "B" Battery
Reproducer
Storage Density Insufficient data given
Reference: Miles Reproducer Company, Inc., 812 Broadway, New York 3, New York
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Type
Recording Process
Description of Process Ink Pen - Paper
(Texas Instruments - Dual Recording Milliammeter Model A)
Geometry Rolled Chart 1001 long, 6"" wide
Time Duration Range
Frequency Response 0 to 6 cps
Total Record Storage Capacity
Dimensions of Recorder 8+r x 91, x lit,
Input 1 ma full scale at 15,500 ohms
Weight 15-1/2 lbs.
Power Supply 50 watts for heater _ower
Reproducer
Chart Speeds 1211 per minute to 12 11 per hour
Chart Speed Accuracy ? 2%
Chart Drive 28 volts do or 115 volts ac motor
Operating Temperature Range - 20? to + 55? C.
Pointer Accuracy ? 5%
Storage Density
Mechanical
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Recording Process
Type
Mechanical
Description of Process Embossing - Plastic Disc
(Sound Scriber Executive Recorder)
Geometry Disc Diameter 61, maximum
Time Duration Range 8 minutes to 30 minutes for
Frequency Response Probably 300 to 2500 cps
Total Record Storage Capacity
33-1/3 rpm speed
Dimensions of Recorder 8-1/2" wide x 6" high x 11-3/Ln deep
Input 25 ohms
Weight 15 lbs.
Power Supply 115 volts 60 cycles 60 watts
Reproducer Included in recorder
Storage Density
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Type
Recording Process
Description of Process Ink Pen - Paper
Mechanical
(Thompson Products Logarithmic Rectangular Recorder Model ASRI-01)
Geometry Rolled Chart
Time Duration Range Not Specified
Frequency Response 100 to 10,000 cps
Total Record Storage Capacity Not specified
Dimensions of Recorder 6011 x 28" x 21"
Input 80 db range 2V full scale at 1,000 cgs
Weight_ Not specified
Power Supply
Reproducer Not specified
Paper Drive Selsyn with 100:1 gear ratio
Resolution Pen position error less than 0.5% of full scale. Chart position
error less than 0.1? on the 2? per inch scale
Paper Speed From 2? to 60? per inch
Maximum Pen Speed 13" per second
Maximum Pen Travel 7-29/32
Storage Density
Reference:
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B. Acoustical Recording Energy Systems: In these systems acoustical
energy is applied to the recording material, and produces the change in
state of the record. Principal types of systems are:
1.
Material Removed from Record
a.
b.
Ultrasonic Cutting Stylus
Sonic Cutting Stylus
2.
Record Material Displaced
a.
b.
Ultrasonic Embossing Stylus
Sonic Embossing Stylus
3.
Record Material Changed in Physical State
a. Contact Stylus - Vibration Sensitive Record - Physical
Change in State
b. Contact Stylus - Chemical Change in State
c. Focussed Ultrasonic Beam - Vibration
(1) Generated by Electromechanical Resonator
(2) Generated by Corona Discharge (Ionophone)
(3) Generated by Gas Explosions
General Criteria - Acoustical Systems
a. Ungrooved or Pregrooved Blanks
b. Stylus Motion - Vertical or Lateral
c. Rheology of Record Materials
d. Type of Stylus Drive
C. Optical Recording Energy Systems: In these systems optical (light)
energy is applied to the recording material, and produces some change in
state of the record. Principal types of systems are:
1. Latent Image Produced on Record
a. Light Beam from Single Fixed Source
(1) Source Intensity Modulated
(a) Incandescent Lamp
(b) Gas Discharge Lamp
(c) Cathode-Ray Tube
(d) Electric Arc or Spark
(e) Luminescent Phosphor
((1)) Type of Exciting Energy
(2) Beam Intensity Modulated
(a) Mechanically varied optical Elements
((1)) Successive Apertures
((2)) Mechanical Shutter
(b) Electrically varied Optical Elements
((1)) Kerr Cell (Faraday Effect)
((2)) Electron or Ion Bombarded Oil Film
((3)) Solid-State Light Amplifier
((4)) Photoelectron Emitter and Luminescent Screen
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(3) Beam Position on Record Varied
(a) Mechanically Positioned Optical Elements
((1)) Moving Mirror
((a)) Type of Mirror Driving Energy
((2)) Moving Lens
((a)) Type of Driving Energy
(4) Source Color Modulated
(a) Electrical Modulation
((1)) Variable Current to Filament
((2)) Variable RF Frequency to Glow Lamp
((3)) Multicolor CRT Phosphors
(b) Magnetic Modulation
((1)) Multicolor CRT Phosphor Selection
(5) Beam Color Modulated
(a) Variable Transmission Filter(s)
((1)) Type of Filter Actuation
(b) Selection of Multiple Filter Elements
((1)) Type of Selection Process
b. Light Beams from Multiple Fixed Sources
(1) Source Intensity Modulated
NOTE: Most of categories in a. can be repeated here, with
addition of systems using multiple-digit codes such
as PCM employs.
c. Light Beams from Multiple Moving Sources
(1) Source Intensity Modulated
NOTE: Most of categories in a. can be repeated here, with
addition of more complex codes such as can be achieved
with multiple-gun CRT sources, etc. Here, formation
of letters and numerals can be included.
2. Visible Image Produced on Record
a. Light Beam from Single Fixed Source
(1) Luminescent Phosphor Record
(2) Direct Printing Photo Materials not Requiring Processing
NOTE: Many of the systems in 1. may be used to excite these
records.
3. Electrical Charge Image Produced on Record
NOTE: In addition to above categories, the element of a two-
dimensional scanning of the record by a portion of its on
system can be introduced since tubes such as the Farnsworth
Image Dissector can produce the record on a mosaic, etc.
4. Chemical Change Produced in Record
General Criteria - Optical Systems
a. Coding System
(1) Variable Area
(2) Variable Density
(3) Variable Color
(4) Combinations of Multiple Sources
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b. Optical Element Drive
(1) Electromagnetic
(2) Piezoelectric
(3) Mechanical
(4) Electrostatic
c. Record Materials
(1) Sensitized Film
(2) Sensitized Paper
(3) Sensitized Plates
(1) Photoemissive Surface
d.
Record Processing After Recording
(1) Type of Processing Energy
e.
Spectral Sensitivity
(1)
Of Light Source
(2)
Of Record Material
(3)
Of Optical System Elements
f.
Light Source Characteristics
(1) Frequency Response
(2) Power Requirements
(a) AC or DC Excitation
(b) RF Excitation
(c) Efficiency
(3) Brightness
g. Type of Light Modulation Energy Supply
h. Response of Record to Signal
(1) Response Time
(2) Persistence or Permanence
(3) Linearity
(a) Linear
(b) Logarithmic
(c) Vector (Tristimulus Diagram)
(.) No. of States per Element of Area
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Type
Recording Process
tic al
Description of Process Light Beam - Photosensitive Record
Mirror deflected by galvanometer type movement
NOTE: Charts need no development or fixing; cannot be exposed to bright light.
Geometry Strip Chart 60 mm. wide x 15 meters long
Time Duration Range 150 seconds at 100 mm./sec. to 500 min. at 0.2 mm./sec.
Frequency Response Upper limit varies from 1 to 570 cycles/sec.
Total Record Storage Capacity Resolution not specified
Dimensions of Recorder Not specified
Input 8 - 4,700 ohms in various models
Weight Not specified
Power Supply 220 volts 50 CPS
Reproducer None specified
Light Source High pressure mercury source (0.3 x 0.3 mm2). Brightness 105 Stilb
Light Power Supply 86 - 100 watts, 16 - 24 V.D.C. Ignition 650 V.A.C.
Ignition Time Several minutes Price $1,025.00
Maximum Trace Velocity 10 meters/sec.
Maximum Sensitivity 1 mm. deflection for 0.03,aa. across 4700 ohms or for
0.038 mv. across 8 ohms
Chart Drive Synchronous Motor Maximum No. Channels 4
Storage Density
Reference: Hartman and Braun A-G, Frankfurt/Main, Germany.
Model RLT4 "Lumiscript".
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D. Thermal Recording Energy Systems: In these systems thermal energy
(including infra eradiation not handled by optical means) is applied to
the record. Principal types of these systems are:
1. Material Removed from Record
a. Evaporation of Record Material
(1) By Stylus Point
(2) By "Flame" Stylus
(a) Gas Flame
((1)) From LPG Container
((2)) From Chemically Generated Gases
(b) Heat from Electrical Discharge
(3) By Electrical Coil Stylus
(4) By Infrared Radiation
(a) From Heated Stylus
(b) From Radiant Energy Source
(5) By Heated Gas Stream
2. Material of Record Displaced
a. By Stylus Point
b. By t1Flame" Stylus
(1) Gas Flame
(a) From LPG Container
(b) From Chemically Generated Gases
(2) Heat from Electrical Discharge
c. By Electrical Coil Stylus
d. By Infrared Radiation
(1) From Heated Stylus
(2) From Radiant Energy Source
e. By Heated Gas Stream
3. Change in Physical State of Record
a. Color Changes
b. Changes in Magnetization
General Criteria - Thermal Systems
a. Ungrooved or Pregrooved Blanks
b. Stylus Motion
(1) Vertical
(2) Lateral
c. Type of Stylus Drive
(1) Electromagnetic
(2) Electrostatic
(3) Piezoelectric
(!t) Hydraulic
(5) Mechanical
d. Records Processed or Unprocessed After Recording
e. Method of Heating Point Stylus
(1) Chemical
(a) Localized Combustion
(b) Exothermal Non-Combustion Reaction
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(2) Electrical
(a) Type of Energy Modulation
f. Thermal Record Materials
(1) Chemically Treated Paper
(2) Synthetic Plastic Materials
(3) Metal Foils
g. Method of Providing Heated Gas Stream
E. Electrical Recording Energy Systems: These systems apply electrical
energy directly to the record material. Principal types of systems are:
1. Material Removed from Record
a. By Corona Discharge
(1) Puncturing of Film Record
(2) Erosion of Record Surface
b. By Spark Discharge
c. By Low Voltage Current Flow
(1) Generation of Heat in Record
(2) Migration of Ions in Record
d. Attraction of Charged Particles from Record
2. Material Added to Record
a. Attraction of Charged Particles to Record
(1) Single Stage Process (Smoke Printing)
(2) Two-Stage Process (Xerography)
3. Record Material Displaced
a. By Corona Discharge
b. By Spark Discharge
c. By Low Voltage Current Flow
4. Record Material Changed in Physical State
a. Latent Image Produced in Record
b. Color Change in Record
c. Change in Index of Refraction of Record
d. Charge Induced on Record
(1) Dielectric Record
(2) Conducting Elements on Dielectric Record
e. Bi-Stable Ferroelectric Elements
f. Electrets
General Criteria - Electrical Systems
a. Ungrooved or Pregrooved Blanks
b. Stylus Motion
c. Type of Stylus Drive
d. Record Processing Required
e. Method of Creating Electrical Energy Output
f. Frequency of Output Voltage (Carrier)
g. Type of Output Modulation
h. Type of Record Material
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Type
Recording Process
Electrical
Description of Process Rotating Helix Electrode - Electrosensitive Paper
Geometry Helix marking perpendicular to direction of paper travel
Time Duration Range 1 hour operation for 90 feet of paper
Frequency Response
Total Record Storage Capacity
Dimensions of Recorder
Input
Weight
Power Supply
Reproducer
Writing Rate 300" per second
Resolution 0.311 paper travel for 3001' writing
Storage Density
Reference: Bulletin Alf ax Paper and Engineering Company
NOTE: Multiple blades or platens and multiple helices can be used for
multi-channel recording.
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Type
Recording Process
Electric
Description of Process Fixed Stylus - Current Sensitive Paper
Geometry Fixed Stylus - Strip Chart
Time Duration Range 3/4 hour to 8 day per 100-foot roll
Frequency Response One event per second for 3/4 hour unit;
one event per minute for 8 day unit.
Total Record Storage Capacity
Dimensions of Recorder Approximately 5" x 2" x 4"
Input
Weight Not specified
Power Supply 110 volts 60 cycles
Reproducer Not specified
Number of Channels 2 on 0.4" tape up to 30 on 5-1/2" tape
Storage Density
Reference: Alden Electronic and Impulse Recording Equipment Company catalog
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F. Magnetic Recording Energy Systems
1. Material Removed from Record
a. By Attraction of Magnetic Particles from Record
2. Material Added to Record
3. Record Material Displaced
4.
Record Material Changed in Magnetic State
a. Orientation of Magnetic Domains - Thin Layer
(1) Variable Density Type
(2) Boundary Layer Type
b. Magnetization of Static Elements
(1) Bi-Stable Magnetic Cores
(2) Multi-Stable Elements (Barkenhausen)
General Criteria - Magnetic Systems
a. Record. Geometry
(1) Drum
(2) Sheet
(3) Disc
(4) Tape
(5) Wire
b. Type of Magnetic Field Modulation
c. Method of Applying Magnetic Field Energy
d. Type of Record Material
(1) Oxide Coated Plastic
(2) Homogeneous wire
e. Type of Coding
(1) Return to Zero Systems
(2) Non-Return to Zero Systems
f. Type of Playback Head
(1) Output Amplitude Proportional to Flux of Record
(2) Output Amplitude Proportional to Tape Speed
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Type
Recording Process
I Magnetic
Description of Process Magnetic Tape
Ampex Model 350
Geometry Tape - Reels 10-1/2" diameter x 1/4" wide
Time Duration Range 32 minutes to 4 hours, 16 minutes
Frequency Response 30 to 15,000 cps +2 db
Total Record Storage Capacity
Dimensions of Recorder Approximately 20" x 140" x 20"
Input 600 ohms balanced or unbalanced
Weight 84 lb s .
Power Supply 110 V 50 or 60 cycles at 2.7 amperes
Reproducer Included in Recorder
Signal to Noise Ratio 70 db to 50 db depending on tape speed
Flutter and Wow 0.2 to 0.3% depending on tape speed
Starting Time 0.1 second
Stopping Distance Less than 2" from 15" per second speed
Playback Timing Accuracy ?0.2% (?3.6 seconds in 30 minutes)
Rewind Time 1401 per second
Storage Density
Reference :
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Type
Recording Process
I Magnetic
Description of Process Magnetic Belt - FM Carrier Recording
Ampex Model 700
Geometry Magnetic Belt !j" wide x 40-1/411 long
Time Duration Range 5 seconds; tape speed 7.5" per second t0.5%
Frequency Response 1-1/2 to 3-1/2 cps (-3db) 3-1/2 to 300 cps (tl db)
Total Record Storage Capacity
Dimensions of Recorder 20" x 16" x 70"
Input 26 Channels 1 V rms across 100,000 ohms; L5 to 50 db above noise
Weight 2112 lbs.
Power Supply 42 amps at 12 V dc
Reproducer Included in Recorder
Output 1 V rms across 1,000 ohm line
Harmonic Distortion Less than 1% ms total at peak recording level
Time Alignment Interchannel Misalignment Does not Exceed 1 millisecond
Storage Density
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Type
Recording Process
Description of Process Bi-Stable Magnetic Cores
I Magnetic
Alden Products Co., Static Magnetic Memory Model 5100RA
Geometry
For Minimum Signal Noise Ratio use Rise Time Should
Time Duration Range Be 5 Microseconds
Frequency Response Can Handle Up To 30,000 Pulses Per Second
Total Record Storage Capacity One Bit Per Unit
Dimensions of Recorder 1-5/8" x i-5/8" x 1"
Input
Weight
Power Supply Driving Tube Must Deliver Peak Plate Current of 150 ma
Reproducer
Storage Density
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Type
Recording Process
Magnetic
Description of Process Magnetic - Wire
(Miniphon)
Geometry Wire 11.8 in./sec. 0.002" diameter
Time Duration Range .25 to 2.5 hours (with different record spools)
Frequency Response 200-4000 cps
Total Record Storage Capacity
Dimensions of Recorder 4-3/8" x 6-5/8" x 1-3/8"
Input Crystal Microphone
Weight 2.125 lbs.
Power Supply 1.5 V A Battery, 30 V B Battery, 9 V Motor Battery
Reproducer Same as Recorder
Output 500 ohms
Motor Battery Life 24 hours
Rewind Speed 2.5 times record speed
No. of Channels 1
Storage Density
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G. Electronic Recording Energy Systems: In these systems energy is
applied to the recording medium by electrons (and for completeness the defin-
ition is expanded to include other elementary charged particles) which have
acquired energy by acceleration from an electric field - normally in a vacuum.
Principal types of systems are:
1. Marking of Record in Vacuum
a. Latent Image - Film Record
b. Charge Image - Secondary Emission by Record
c. Charge Image - Accumulation of Charge by Record
d. Photosensitive Record - Charge Image
e. Bombardment of Record by Radioactive Ions
f. Chemical Reaction of Record with Incident Ions
2. Marking of Record in Air
a. Charge Image - Exterior of Dielectric Bombarded by Electrons
General Criteria - Electronic Systems
a. Type of Coding System
b. Method of Producing Accelerating Field
c. Source of Charged Particles
d. Record Processing After Recording
e. Response of Record to Signal
(1) Response Time
(2) Persistence or Permanence
(3) No. of States Per Element of Area
H. Electromagnetic Recording Energy Systems: The recording media for
these systems are sensitive to electromagnetic radiation. Two sources are
excepted, visible light and radiation from nuclear disintegrations, since
optical and nuclear techniques differ radically in practice from techniques
of handling electromagnetic energy.
NOTE: After review of possible systems in this category, it appears desirable
to include the few possible systems under other categories (e.g. under
nuclear systems for gamma rays and electrical or optical systems). Until
very short wavelengths are reached, electromagnetic fields are not capa-
ble of sufficient resolution to be very useful. It is true that very
short waves (overlapping infrared wavelengths) have been produced,
but these are presently derived from weak harmonics of reflex klystrons,
with very low power conversion efficiency. Combinations of electric
and magnetic fields may be quite useful, but these are not strictly
electromagnetic systems.
I. Nuclear Recording Systems: In these systems energy derived from a
nuclear source is applied to the recording medium. This classification does
not include radioactive materials transferred to the record by mechanical or
other means. Principal types of nuclear systems are:
1. Latent Film Image Produced on Record
a. Nuclear Emulsion Record
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(1) Natural Radioactive Source
(a) Alpha Particle Emitters
(b) Neutron Sources
(c) Beta Ray Emitters
(d) Gamma Ray Emitters
((1)) Moving Stylus in Contact with Record
((2)) Nuclear Energy Beam from Single Fixed Source
((a)) Intensity Modulation of Beam by Signal
(((1))) By Mechanically Positioned Absorber
(((2))) By Electrically Varied Aperture
b. Other Nuclear-Sensitive Emulsion Records
c. Non-Emulsion Records - Latent Image
2. Radiation Damage Produced in Record
3. Radiant Energy Produced in Record
4. Electrical Charging of Record Elements
5. Chemical Effects Produced in Record
General Criteria - Nuclear Systems
a. Type of Coding System
b. Radioactive Element Drive
c. Types of Record Materials
d. Record Processing After Recording
e. Nuclear Source Characteristics
f. Type of Nuclear Beam Modulation
g. Nuclear Beam Modulation Energy Supply
h. Response of Record to Signal
(1) Response Time
(2) Persistence or Permanence
(3) Linearity
(L) No. of Physical States per Element
i. Type of Reading Energy
J. Chemical Recording Energy Systems: As defined these systems apply
energy to the recording material primarily in chemical form. The original
means of bringing chemical energy to the record may involve mechanical trans-
port, but the end effect is a chemical reaction.
1. Solid Added to Record
a. Etching or Corrosion of Record Surface
(1) Unselected Record Surface
(2) Chemically Treated Record Surface
b. Color Change of Record Surface
(1) Color of Applied Material Changed
(2) Color of Record Material Changed
2. Liquid Added to Record
a. Type of Chemical Reaction Produced
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(1) Oxidation
(2) Reduction
(3) Polymerization
(4) Depolymerization
(5) Bond Formation
(6) Bond Disruption
b. Physical Reaction Produced
(1) Formation of Gas Bubbles
3. Gas Added to Record
(Similar to
14. Contact of Catalyst with Record
a. Latent Image Produced in Record
5. Removal of Chemical from Record
General Criteria - Chemical Systems
a. Ungrooved or Grooved Blanks
b. Stylus Motion - Vertical or Lateral
c. Stylus Drive
d. Record Processing After Recording
e. Chemical Source Characteristics
f. Type of Chemical Stream Modulation
(1) Reagent Injected into Gas or Liquid Stream
g. Chemical Carrier Stream Energy Supply
h. Response of Record to Signal
i. Type of Reading Energy
j. No. of Stable States per Element of Area
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VI. Critical Evaluation: With all the factors to be considered, one may
still reduce the recording problem to elementary questions of how to mark
the record and how to drive it. Ignoring such refinements as coding, one
might review principal sources of marking energy as follows:
A. Hypothetical Problem: Provision of a subminiature, rugged, record-
ing device which can e use with a variety of input units in a simple manner.
The recorder should be extremely straightforward in design, with a minimum of
adjustments, but information need not be instantly readable from the record
by eye. The reader can be as complex as desired, and one reader can be used
to service many recorders.
Some tentative specifications may be set up:
1. Duration of Recording: At least 30 minutes.
2. Frequency Response: 0-2500 cycles per second.
3. Total Storage Capacity: About 107 bits.
la .. Power Supply: Self-contained.
5. Weight: Not more than 1 pound.
6. Dimensions: Not greater than 3/4" x h" x 5".
7. Input: 1volt across 600 ohms (rms).
8. Accuracy: 2% of full scale.
B. Problem Discussion: With severe space and weight limitations, the
power supp y for recording and scanning energy is a critical factor. In
this case possible principles of use for recording may first be examined to
find those with the lowest energy requirement. Because of the limitations
of this study, review will be made only of possible optical, nuclear, and
chemical systems of novel types which might fulfill the requirements.
C. Possible Optical Systems: Photographic film is available in color
with a resolving power of about 60 lines per mm. and in black and white with
135 lines per mm. for microfile and more than 1,000 lines per mm. for high
resolution plates. The exposure time or light intensity requirement increases
for higher resolution film, so that one best compromise exists between the
maximum number of bits per square inch which can be stored, and the energy
required per bit of information.
Possible storage density on microfile is about 107 bits per square inch, so
that one square inch can meet our rough specification. However the size of
an element of area is about 0.0003 inch, and mechanical positioning to this
accuracy would be difficult to realize in production.
Light sources constitute something of a problem in such recording. Incan-
descent sources have poor frequency response and low efficiency. Glow
discharge sources have low brightness. Although a few new types of sources
have been developed in recent years, there is a great deal of promise for
new ideas.
One system which might offer promise would use the old "Crosley tuning
indicator" principle, where the length of glow discharge in a long, thin
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light source was made proportional to signal amplitude. This would eliminate
mechanical motion of film, and would lend itself to a sampling technique
where the lamp was pulsed only at intervals according to the signal. Since
motion of the leading edge of a light source is involved, conversion of
analog to digital information might be achieved, or a multiplicity of colors
might be worked out.
An alternative system is use of the "glow transfert' principle now used in
counter tubes. If each electrode represents a "decade" of voltage values
(i.e. electrode #1 represents 0.01 to 0.1 volt; #2, 0.1 to 1.0 volt; etc.),
then a single tube becomes a 10 per cent recorder over a wide range of
values. Its image could be directly focussed on film.
Still another system would use a binary code wherein each glow lamp represen-
ted one binary digit. With six lamps, sixty-four different values can be
registered, giving an accuracy of better than 2 per cent of full scale.
Mechanical systems of interrupting or moving light beams do not look attrac-
tive from the energy standpoint, except for the fact that transistor ampli-
fiers now allow more efficient driving of low impedance systems than previously.
The very fact that mechanical systems are relatively low impedance systems
seems to imply appreciable power requirements.
Electronic means of generating light are attractive, although development
costs may be relatively high. The "glow modulator" type of tube for sound
on film recording presently has high power requirements, although frequency
response is quite good. So far as is known, no attempts have been made to
miniaturize this type of recording element.
To date, record materials not requiring processing have not been found with
high sensitivity. A search along these lines might be useful, although
record processing might be made so convenient as not to constitute a serious
difficulty.
D. Possible Nuclear Systems: Supplying the recording energy by nuclear
sources is attractive from the standpoint of power supply requirements. One
basic form of recorder might involve a moving stylus where the point is
composed of sufficient radioactive material to make a developable trace on a
film chart at the highest writing speed required.
A system of this sort, involving mechanical motion, might be capable of
attaining the desired frequency response, even if contact with the record
is essential. Small galvanometer elements can be vibrated over limited
amplitudes up to rather high frequencies, and if a collimated beam of nuclear
radiation could be attained with small mass, the system might be feasible.
Necessary amplitude of motion is of course a function primarily of beam width.
So many radioactive materials are available that it is desirable to make a
detailed review of this subject.
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E. Possible Chemical Systems: Suppose that the record in a system
consisted of a spool of nylon thread with diameter just sufficient to
insure a reasonable margin of mechanical strength. (Glass fiber reinforcing
might assist in this respect, if feasible.) If this thread could be marked
(recorded on) in some manner with greater resolution or with less power
requirement than is possible for magnetic wire, a useful system might result.
One conceivable marking system might involve directing a stream of a suitable
chemical gas against the thread. Resolution in a magnetic system is limited
partially by the "granularity" of the record and partially by the area into
which sufficient lines of magnetic flux can be concentrated. The same sort
of limitations might apply to the "nylon thread" system, with resolution
limited by the area into which a suitable gas flow could be concentrated.
It seems possible that more energy per unit area could be obtained from a
chemical gas stream, even allowing for flow effects caused by motion of the
thread.
Chemical reactions for this purpose might be studied, with emphasis on marking
gases which could be stored in liquefied form in a small pressure chamber.
Modulation of the gas stream might be achieved by a tiny, high speed valve,
or by small amplitude motion of the stream outlet. (In the latter event,
recording only of "axis crossings" seems to be a natural feature.) Bromine
may be a possibility.
Sources of chemical energy for marking are attractive from the standpoint of
power supply considerations. The energy per unit volume which can be stored
chemically is normally higher than can be stored electrically. The chemical
fuels are of interest, but thought should be given to "high energy" materials
such as explosives, as well. Other violent or reactive chemicals might be
useful for chart recording on ordinary paper when. used in place of ink. Of
course special materials (e.g. dyes) might be incorporated in the record
material. Prospects for low granularity of records appear encouraging.
Charged cartridges of pressurized gases should be able to be handled as
easily as batteries.
The possibility of using only a catalyst to affect a chemical reaction which
might then take place in the record medium is of interest because a stylus
point of catalyst material might need replacement only occasionally. This
would assist in reduction of power supply requirements.
F. Record Geometry and Scanning: Regardless of the type of recording
energy used, a method of scanning the record must be selected, as well as
the record geometry.
The most practical commercial recording form seems to be the belt as used
by Dictaphone (See Appendix D). If 10 square inches of belt surface is
needed, the length and width of a "square" belt can be 1.75 inches. Present
Dictaphone belts have a width of 3.5 inches and a total area of roughly
42 square inches.
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A miniature belt chart record might first be visualized as a belt having a
diameter of 3 inches and an equal width - perhaps with sprocket holes for
indexing purposes. The belt geometry allows good tracing with linear motion
of the recording head, and a helical track, using the area rather effectively.
On this basis it would be necessary to store 9 x 106 bits in an area of 27
square inches, or 3.3 x 105 bits per square inch. The linear dimension of a
bit is .00175 inch, so that the speed of the belt will need to be about
8.8 inches per second. For a 1 inch circumference driving drum, this would
correspond to about 510 rpm. The power requirement for 1/2 hour at this
rate might be excessive. A clockwork motor might be hard-pressed to supply
this much energy.
Drive: The Esterline-Angus chart recorder uses a spring clock in some models,
antic will drive a rather large chart and take-up mechanism at speeds up to
6 inches per minute for as long as 4 hours, almost the equivalent of 48 inches
per minute for 30 minutes. The Esterline-Angus escapement design is not new,
and modern techniques might bring the drive speed of a much smaller chart
(less take-up mechanism) up to perhaps 100 inches per minute for 30 minutes,
while reducing size and weight.
Thus, 1.67 inches per second seems reasonable, and this is within a reasonable
range of a belt diameter which does not place too severe tolerance require-
ments on the mechanical system.
Another good form of geometry is the wire (or thread, as previously mentioned).
The "Miniphone" recorder can achieve a response of 4000 cps with 11.8 inches
per second of 0.002 inch diameter steel wire. Experience at SwRI indicates
that tungsten wire with a diameter of 0.0002 inch might be handled success-
fully from the mechanical standpoint. If chemical or optical marking of this
wire could be achieved with a resolution of 100 lines per mm. or 2500 lines
per inch, then a tape speed of 2 inches per second would be necessary for 2500
cycles at two bits per cycle. For 30 minutes, a length of 3600 inches or
300 feet would be needed; this would occupy a volume of (-0(.0001)2(3600)
or roughly 10-4 cubic inch. A minimum spool diameter of perhaps 0.75 inch
would be needed to avoid crimping the wire around a sharp bend.
G. General: In examining all possible systems to arrive at the better
prospects,, it is necessary to develop weighting factors for the important
criteria. This raises many questions:
Consider the factor of resolution. This is involved with the minimum area
or volume in which one or more bits of information may be stored. Yet the
interrelation of limitations on resolution and those on area cannot be
avoided. A high resolution system might be realized, for example, by causing
the deposition of atoms of various stable isotopes to be arranged in a
crystal in a certain way. The number of bits per atom would depend on the
number of stable isotopes which could be detected by the beam of exploring
energy (reading energy), or by the amount of energy available for creating
the isotopes initially. Since the wavelength of an energy beam is always a
measure of its energy level, it is fair to assume that high resolution will be
associated with a high energy level. This does not necessarily mean a high
power input if the energy is efficiently used.
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VII. Bibliography: While a bibliography was recently published by Hollander,
it does not contain data on many of the basic principles necessary to evaluate
recording processes. Energy conversion principles are not treated well in any
known papers. With the budget limitations of this present study, it was not
possible to conduct a proper literature or patent search, but this should
certainly be done. In particular, a careful review of ASTIR items should be
made.
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Energy Conversion Processes and Recording
For basic analysis it is necessary to consider recording as an energy con-
version process. Energy from an information source plus (in most cases)
energy from local power supplies are directed to a volume element of the
record, and it must be assumed that in all cases that element represents
a higher energy level when it stores information. Reading must direct a
second quantity of energy to the element of the record.
There is, therefore, an energy conversion efficiency factor which must
describe one of the most fundamental properties of a recording process. In
addition, the resolution of a process must be closely associated with the
volume required to store the smallest amount of energy which can be
detected (in a given time, and with a given noise figure) by the reader.
Thermodynamic concepts of ewtropy and energy should be explored specifically
in this connection.
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Communications Theory and Recording
D. K. C. Macdonald) suggests that the entropy of a system be regarded as
a measure of its overall state, while information should be regarded as
an incremental quantity characteristic of a transition or possible transition
from one state to another. Then in communications
112=-4S12
where InS12 is the change in entropy.
Starting with knowledge of the statistical structure of all possible
messages to be recorded, and the requirements for message readout, it is
possible to design a recording system which is neither too elaborate nor
too simple for a very high percentage of possible messages. Even as
0. H. Schade developed "equivalent bandwidth" concepts for optical elements
of TV systems, so will it be possible to treat mechanical tolerances and
other fundamental system limitations in such a manner that individual elements
are not overdesigned.
1JAP May 1952.
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Mechanical Tolerances in Recording
For any recording system involving mechanical motion, a limiting factor in
resolution, recording time, or other performance variables is mechanical
tolerance. The familiar example of mechanical precision has been the ruling
engine for diffraction gratings, which has required large mass, isolation
from vibrations, thermal stability, aging of metal parts, and other extreme
care in construction to realize the capabilities of resolution within
optical dimensions. Lately, elaborate feedback systems have been used to
correct for some process variables.
Extremely compact recording systems must be so designed as to minimize the
effects of mechanical variations and to use ordinary fabrication methods.
For this reason, careful study should be given to systems not requiring
mechanical positioning of elements, or which can incorporate very simple
servo correction systems. At the same time, data should be obtained on the
realistic limits of present shop practice, where servo controls of machines
may raise ordinary standards. Little attention seems to have been paid to
the limitations imposed on recorders by these factors.
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APPENDIX D
Record Geometry
Since it is possible to use three-dimensional spaces to store information,
these should be considered in a general analysis. However, the great
majority of existing recording media use the third dimension only inci-
dentally or not at all. The common forms of records, and the two- and
three-dimensional spaces they occupy, are listed in Table II which follows.
Practical
Form of Record
Equivalent
Solid
Scanning
Axes
Equivalent
Area
1.
Wire
Cylinder
Z
Rectangle
2.
Belt
Cylinder
D,Z
Rectangle
3.
Cylinder
Cylinder
o,Z
Rectangle
4.
Disc
Cylinder
..,O
Circle
5.
Tape
Parallelopiped
Z
Rectangle
6.
Chart
Parallelopiped
y,Z
Rectangle
7.
Sheet
Parallelopiped
y,Z
Rectangle
8.
Magnetic
Core
Parallelopiped
x,y,Z
--
Matrix
9.
Mobius Strip
?
Table II
Solid Geometry of Records
D-1
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An analysis of the maximum recording space that can be made available with
specified limitations can be made using the principles of analytic geometry.
For example, if the "maximum dimension" of the record (for a given storage
capacity) is critical, a drum may be preferred to a disc. Using only one
side, a drum has a surface area of 7rDW square inches, where D is the drum
diameter and W is the width. If W = D (for the smallest maximum dimension),
then the area is 7lD2. A disc with the same maximum diameter D has an
area only of 7rD2/)1, so that the drum has four times the disc area.
On the other hand, if a "thin" package is desirable (with one small dimension)
the disc and belt may be compared. In a volume of, saytt 11, x 41, x 5",
the largest disc would have an area (one side) of 7TD2/L = 47r. A belt
running on two pulleys of diameter d = 1" and w = 5" could have a separation,
S, of pulley centers of 3", and its length L would be L = 2S + Td, or
(6 + rr) inches. Thus the belt area would be (6 + 7r)5 or 30 + 5-rrinches2.
Scanning Geometry: In two-dimensional cases, it is possible to scan a
given area in many ways. Some common types of scanning are:
1. Single Line Scan
2. Parallel Line (Raster) Scan
3. x-y Scan
Ii.. Parallel Circle Scan
5. Spiral Scan
6. PPI Scan
7. Sound Track (Variable Area) Scan
Decision as to the most efficient scan for a given recorder design has
usually been dictated by record drive problems. Since the reader must be
made to follow the same path as the recorder in many systems, a continuous
rather than an intermittent path has often been preferred. This does not
necessarily make most efficient use of the area, For example, the constant
pitch spiral used in disc recording separates all tracks by the minimum
amount necessary to achieve a certain cross-talk figure, so that storage
density is sacrificed for simplicity.
Mark Geometry: The shape of an individual mark made on the record by the
recordll_j "stylus" is not simple. For example, in an embossing process
such as the plastic belt "Dictaphone" system, the width of the groove may
be less than the stylus width because of the elasticity of the material.
As the stylus plows through the record there is a "bow wave" ahead of the
stylus which modifies the trace of the stylus in some way.
The "mark" in a flying-spot scanner recording, say, on film may be quite
complex. 0. H. Schade studied cosine-squared and exponential aperture
response factors since the distribution of light in a cathode-ray tube
spot is far from uniform over a circular area. Fringing effects modify
the pattern of a magnetic flux gap.
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Resolution of any recording process is degenerated by the effective geometry
of the mark on the record. The usual type of mark is a "spot" or a "slit,"
ideally. For each type of recording system the mark geometry must be a
major factor in evaluation.
D-3
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A study of record materials must be made independently for each type of
recording energy. The sensitivity of a material to this energy is a vital
factor in energy economy, and each material may have an equivalent ttnoise
figure" of its own, depending on the dynamics of the recording process.
The number of energy levels or stable states of an element of record area
offers a potential opportunity to improve recording efficiency very sub-
stantially. Color film can store as many elements as can be recognized by
the optical reading system. It is possible to visualize the equivalents of
"colors" in magnetic or chemical or nuclear systems. This property of
record materials should be carefully explored.
Processing of records after recording should also be explored. This apparent
disadvantage to practical operations may nevertheless afford very substantial
economies in expenditure of recording energy. Such processing could actually
be performed in the recorder itself, by applying uniform energy per unit
area, at less overall energy expense than if signal energy alone is used.
This is because the conversion of power supply energy to signal energy is
often extremely low.
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