TELETYPE STUNT BOX

• Document Type: CREST
• Collection: General CIA Records
• Document Number (FOIA) /ESDN (CREST): CIA-RDP78S05452A000100040010-2
• Release Decision: RIFPUB
• Original Classification: K
• Document Page Count: 20
• Document Creation Date: December 9, 2016
• Document Release Date: March 23, 2001
• Sequence Number: 10
• Content Type: REPORT

 Approved For Release' 200,140,7,f%
II
introduction THE BIG PLUS
applications SELECTIVE CALLING
EQUIPMENT APPLICATIONS
REMOTE CONTROL
functions BASIC FUNCTIONS
basic operation ELECTRICAL PULSES
STUNT BOX LOCATION
FUNCTION MECHANISM
(basic components)
FUNCTION MECHANISM
(cycle of operation)
components detailed FUNCTION BARS
PAWLS and LEVERS
COMPLETE STUNT BOX
detailed operation FORKS, SLIDES, SWITCHES
(latching-unlatching)
SELECTIVE CALLING
(terminology)
SELECTIVE CALLING
(in action)
? 1959 by TELETYPE CORPORATION Approved For Rele
The age of commercial jet air travel is
here. It has brought with it the need
for even faster, more efficient nation-
wide communication of weather data,
flight plans, and routine message traffic.,
From the local level to central control,
Teletype supplies equipment that helps
meet this need.
Automatic polling of outlying stations
includes the utilization of the "stunt
box" in assimilating and disseminating
weather information and other air traffic
data faster than ever before.
r,'PAGE
PUNTER
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introduction
THE BIG PLUS what it is, what it does ...
This brochure is the story of "more value" . . . a
"BIG PLUS" feature of Teletype Model 28 equip-
ment. It is the factual story of a "futuristic,"
component assembly called the STUNT BOX.
One of the most outstanding characteristics of
100 word-per-minute, Teletype Model 28 equip-
ment is its versatility ... achieved to a great
degree by this stunt box.
Contained in a lightweight aluminum housing
within the typing unit, the stunt box is 9A " long,
4Y " wide and 2% " high. Compactly arranged, it
is the key to an entirely new control concept in the
field of record communications.
How does the stunt box affect
page printer operation?
Early teletypewriters had two shift positions.
One was the "Letters" case, which allowed the
operator to use 32 combinations of the conven-
tional, 5-level, Baudot, telegraphic code for
printing 26 letters of the alphabet and performing
6 related functions. The other was the "Figures"
case, or shift position, for printing numbers,
symbols and performing functions-also utilizing
the same 32 code combinations.
Early equipment, however, was limited in scope
of operation because among other things, when
additional special non-printing functions were
required, it was often necessary to sacrifice
printed characters.
To overcome this inadequacy, the Teletype
Model 28 page printer stunt box provides a "BIG
PLUS" third shift feature, which enables the 32
combinations of the "Letters-Figures" shift con-
ditions to be again reused to perform special non-
printing functions, without ever sacrificing a
single printed character.
Also with early equipment, only one character
could be assigned to perform a single function.
With the Model 28 stunt box, a single character
into a code sequence to perform a single function.
These aids to printer operation, while im-
portant, are only a small part of the capabilities of
this unique assembly. Serving as an automatic
control device for local and remote operations,
responding to keyboard or line signals, the stunt
box is actually a built-in sequential selector.
Literally, this means the stunt box serves as a
memory storage medium, with a mechanism for
translating discrete electrical pulses into mechani-
cal motion. This motion, in turn, further initiates
mechanical or electrical actions to perform desired
operations.
The remote control applications of the Model 28
stunt box alone are becoming so popular that a
special self-contained, sequential selector unit has
been perfected just for this purpose.
Major use of this dynamic unit is concerned with
"selective calling" and "integrated data process-
ing" applications. In any situation requiring re-
mote control, the Teletype Model 28 typing unit
with its stunt box can perform tasks usually as-
signed to costly, more complex, larger equipment.
Utilizing the stunt box, operational procedures
in both large and small communication networks
can be simplified, equipment bulk can be reduced
How the stunt box
got its name
In the early days of printing
telegraphy, "stunts" was the
term applied to nonprinting
functions. These functions were
actuated by function or "stunt"
bars in the function assembly
of printing telegraph equip-
ment.
Early use of the term
day designation of the function assembly as a
"stunt box."
What can the stunt box do?
New uses have been found for this flexible, ver-
satile unit faster than we've been able to list them.
From present indications, the variety of applica-
tions for this control mechanism will continue to
be limitless.
Basically, the stunt box will perform the follow-
ing operations:
1 Mechanically initiate internal functions
within the typing unit of the page printer
set.
2 Electrically control functions within the
page printer set.
3 Electrically control external equipment.
What does this mean?
Let's consider a hypothetical situation:
Suppose you were a midwesterner who liked to
drink hot coffee in the morning just after arrival
at your office.
You could arrange to have your New York
operator (who, due to time differences would
begin an hour earlier than you) send a signal at a
specified time daily. This signal would cause the
programmed stunt box in your Teletype printer to
operate a switch controlling a coffee percolator.
Upon arrival at the office, you
could begin your business day
with hot coffee, cup in hand.
We mention this seemingly
whimsical example only to point
out the fact that ... utilizing
the stunt box ... anyone can
do anything from turning on a
coffee percolator at a remote
location, to calling in an entire
network of stations from coast
can be used or several charactApprovecd? Or' elease /07% &eed I~a' '3 4 1 0 116- 1?ast'
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SELECTIVE CALLING ... inter plant or intra-plant
INTER-PLANT
The most popular application of the stunt box in communications
and data processing is its use as a sequential selector for message
directing.
Consider a nationwide inter-plant network consisting of Teletype
Model 28 equipment. Circuits for this system can be established
through the stunt box in a variety of ways. One city can call all
other cities simultaneously ... individually ... or in groups of
2, 3, 4, etc. A detailed description of how this is accomplished is
found in a special section of this brochure devoted to SELECTIVE
CALLING functional operations. (See pages 16 and 17.)
,,TIZOIT
YORK
INEW ORLEANS
INTRA-PLANT
The same procedure can be applied to an intra-plant operation
with page printers or automatic send-receive sets located in spe-
cific departments, such as:
A
The principal advantage of these systems is that message traffic can
be selectively directed only to those printers actually concerned with
the information being transmitted. Printers in the system that are not
called in are always "alert", their stunt boxes continually "riding-
the-line," waiting for specific information to be directed to them.
When the stunt box recognizes a control signal directed to its printer,
a "lightning" chain of events begins, allowing the selected printer
to start operations.
RECEIVING 19 ACCOUNTING
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applications
EQUIPMENT APPLICATIONS ... all involve stunt box use
To illustrate an example of selective calling in actual business
practice, let us consider an integrated data processing system. An
operator at the keyboard of a Teletype Model 28 page printer or
automatic send-receive set, completely fills out a SALES order.
As she enters information onto the form, the stunt box auto-
matically and selectively directs pertinent information to those
specific departments concerned with the particular information
being entered. For example ... every department would get the
order number, while cost information would be received only by
ACCOUNTING, BILLING and MANAGEMENT.
In conjunction with IDP applications ... when a Teletype
printer is equipped with a sprocket feed platen for multi-carbon
forms ... the stunt box activates the operation of such required
functions as horizontal tabulator, vertical tabulator and form
feed-out.
Other equipment applications include automatic switching, code
conversion (sequential signals to multi-wire output), digital tele-
metering, control of mechanical production in the "automatic
factory," error checking and a variety of special uses. A typical
example of a special use is an application where the stunt box is
used to "trigger" an answer back unit that sends a message veri-
fication character to the sending unit.
POPULAR APPLICATIONS
The selective capabilities of the stunt box as
well as all of its other operations can be
tailored to your individual needs. You have
only to define what you would like it to ac-
complish . . . Teletype engineers will be
pleased to show you how the stunt box can
fulfill your requirements. Approved For Release 20
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applications
REMOTE CONTROL ... controls electrical equipment anywhere
OPERATOR AT
KEYBOARD CONTROLS
TELETYPE MODEL 28
TAPE READER
In addition to its use in selective calling and integrated data
processing, another major application of the stunt box is con-
trolling auxiliary apparatus. In this category is the control of
Teletype tape punches, readers and business machines of all kinds.
Stunt box action can tell one machine to record on tape, another
to record on a form, and others to "listen" but not record.
TELETYPE MODEL 28 MISCELLANEOUS
TAPE PUNCH EQUIPMENT
Unlimited applications of the stunt box are possible through
its ability to close and open electrical contacts for equipment
such as alarms, signal lamps, signal bells, and motor controls in
remote locations. Illuminate an area, increase pumping pressure,
start a computer ... all these, and many more, actions can be
accomplished at the same time, on the same circuit-with each
machine responding only to its own instruction through stunt
box control.
In conjunction with remote control as related to various busi-
ness machines ... through stunt box use, sequential signal input
to the printer can be converted to multi-wire output for use by
auxiliary equipment. An enormous field of application is opened
by combining systems when this feature is employed with available
commercial data processing equipment.
When considering remote control equipment it should be remem-
bered that the Teletype Model 28 stunt box can start or stop any
electrical operation controlled by a switch.
The stunt box is
considered the
"robot brain" of the
units shown here.
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BASIC FUNCTIONS...
make possible a variety
of applications
Physically surrounded by the framework of its aluminum housing,
the stunt box is provided with forty two code slots. Each of these
slots will accommodate a function mechanism that is designed to
perform a specific function.
As stated earlier, the stunt box will perform three basic func-
tion operations-internal mechanical ... internal electrical ...
and external electrical. These operations can be accomplished
individually or simultaneously, depending on how the stunt box
function mechanism has been coded, "set up," or programmed.
Normally, six of the stunt box's code slots are assigned to
standard nontyping printer functions ... they are:
1 Letters Shift 4 Line Feed
2 Figures Shift 5 Blank
3 Carriage Return 6 Space Suppression for Line Feed
Besides the six basic essential nonprinting functions, a number
of additional functions may be introduced. With modifications to
the basic function mechanisms, and with additional parts placed
in the remaining open code slots, the following functions may be
performed:
1 Automatic Carriage Return
and Line Feed
2 Unshift on Space
3 On-line Backspace
4 Horizontal Tabulation
5 Keyboard Lock
functions
6 On-line, Reverse Line Feed
7 Form Feed-out
8 Signal Bell Contact
9 Busy Light Contact
10 Motor Stop Contact
11 Vertical Tabulation
The necessary parts can be supplied to equip your Teletype units
for handling any desired additional functions. To increase versatility,
field conversions may be made in which completely different stunt box
arrangements are interchanged.
The Sequential Selector
The popularity of utilizing the stunt
box as a control unit even where the
page printer is not required, brought
about the development of the Teletype
Model 28 sequential selector. This unit
is similar to the page printer typing
unit except that the printing and paper
handling mechanisms have been
removed. It is exclusively used in
remote control operation.
sequential selector.
This unit is activated by
incoming sequential signals.
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basic operation
Pulses originate
at keyboard
ELECTRICAL PULSES ... how a message is sent electrically
Pulses received
and converted to
tape intelligence
Teletypewriter equipment is unique in that it permits the
instantaneous delivery of printed messages regardless of
the distance they must travel.
This is of course possible because these messages are
transmitted in the form of electrical pulses-which travel
with the speed of light.
When the contact in the signal line is closed, current flows and
the line is said to be "marking." A MARKING PULSE is gen-
erated when the contact is held closed for a fixed length of time.
0 0 000. 00 0
000 00'' 0 0 0 0 0 0
0 0 00 0 ?0 a0
2 3
SPACE SPACE
0 0000 00
0 0 0 00
Mai
In addition to the code pulses, (which transmit the
message) each combination is preceded by a start
pulse (always spacing) and followed by a stop pulse
(always marking) for synchronization.
0 0 0 0 0
00 . 00 000
? ? ? ?' ? ? ? ? ? 0,0 ? ?
0? 0
000
0 0 0 0 0 0 00
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One of a Variety of Teletype Equipment Coding Arrangements
A pulse is simply a unit of time during which the flow
of current in the signal line is either permitted to continue
-or is interrupted-by the operation of a contact.
Messages originate with keyboard action or transmis-
sion from a tape reader. Mechanical actions are converted
into electrical pulses for transmission over telephone or
telegraph lines and through radio facilities.
IR
When the contact is opened, no current can flow and the line is
said to be "spacing." A SPACING PULSE is generated when
the contact is held open for a fixed length of time.
5
SPACE
Each character in a typical code consists of five Using the letter "D" as an example, pulses one and
electrical pulses which may be either marking or four are marking while pulses two, three, and five
spacing. Red indicates a marking pulse, white a are spacing.
spacing pulse.
Illustrated at left is ,a typical coding arrangement
as used in punched paper tape. "FIGURES"
refers to the character indicated on the upper
portion of a Model 28 key top. "LETTERS" refers
to the character indicated on the lower portion of
the key top. RED DOTS indicate marking pulse
transmission. WHITE DOTS indicate spacing
pulse transmission. (Black dots are feed holes).
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STUNT BOX LOCATION ... relationship to typing unit code bars
We already know that the seemingly magic-like stunt box
is a compact control mechanism measuring 9% 'by 4Y2 'by
2% " over-all.
Now let us relate the stunt box to the position it occu-
Rear view of Teletype Model 28 typing unit
with area occupied by stunt box shown in red.
Actual Operation
With an understanding of the relationship of the
stunt box to the code bars we can proceed with
the mechanics of actual operation.
All operation begins with the receipt of a signal
. i.e., series of pulses-"marking," or-"spac-
ing." This signal is received by the selector mecha-
nism of the typing unit. It is converted into
mechanical action within the typing unit. Link-
ages activated by this action, position five equally
notched bars, called code bars, to the left if the
pulse is marking or right if the pulse is spacing.
pies when performing all of its "magicianly" tasks.
The stunt box extends across the full width of the
Teletype Model 28 typing unit of the page printer,
automatic send-receive set and sequential selector.
Rear view of typing unit with stunt box re-
moved. Code bar assembly is shown in green.
Actually there are nine code bars, five for intel-
ligence others for functions. From top to bottom
they are identified in the illustration at right.
The rear portions of the code bars are identically
notched. Because some code bars will be posi-
tioned to the left and others to the right, the
vertical alignment of both projections and slots
will present a staggered pattern. This over-all pat-
tern changes with the receipt of each variation in
signals received.
Let us now determine how this action affects
actual stunt box operation.
Partial section of typing unit in perspective shows
stunt box in red and code bars in green. The two
fork-like projections on top of the stunt box are
called "shift forks." Shift forks position Suppression,
Zero, and Figures-Letters Shift code bars through
studs.
.a-- COMMON
f- ZERO
FIGURES-LETTERS SHIFT
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basic operation
FUNCTION MECHANISM... basic components
As previously stated, the stunt box has forty-two
code slots. They are marked at 10-20-30 and 40
slot intervals as viewed from the rear.
Consider one opening or code slot in the stunt
box ... let's see how its function mechanism is
affected by the code bars.
The projections at the front of the function bar
are called tines. The illustration below shows a
partial top view of the code bars and two func-
tion bars.
Viewed from the side, in a cut-away drawing of
the stunt box code slot ... the function bar, pawl
and lever are related to each other as follows:
TOP VIEW
Selected function bar
(Completely forward)
TOP VIEW
Unselected function bar
(Forward motion blocked)
The motion of the function bar is initially forward
and then to the rear. If code bar projections do
not block function bar tines, the function bar
moves completely forward. If code bar projections
block function bar tines, forward movement is
stopped.
A function bar front end as viewed from the
rear of the code bars will show tines angled to
Stripper Blade
To this view we shall
add the STRIPPER
BLADE which extends
along the rear length
of the stunt box. The
motion of the stripper
blade is first down and
then up.
Function Reset Bail
To this view we shall
also add the FUNC-
TION RESET BAIL
which moves forward
and to the rear, mak-
ing contact with the
lowest forward projec-
tion of the function bar.
Movements of the stripper blade and the function
reset bail are controlled by linkages to the main
shaft of the typing unit. Their complete cycle of
operation is based on one revolution of the main
shaft.
This view illustrates atypical stunt box
mechanism in an engaged position.
We know that the code bars are positioned depending
on the signal received. Now let us follow the simple
operation of the stunt box mechanism from a
disengaged position to an engaged condition and back
in to a position of rest.
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are called marking tines, those to the right are
called spacing tines.
A fully loaded or "universal" function bar con-
tains sixteen tines (eight "marking" and eight
"spacing"). Tines can easily be removed from the
universal function bar so that it will operate on
any desired code.
This is a Function Pawl
The function pawl is engaged by the rear upper
projection of the function bar.
This is a Function Lever
The function lever is engaged by the function
pawl.
This view illustrates a typical function box
mechanism in a disengaged position.
 FUNCTION MECHANISM ... cycle of operation
1 The function reset bail holds the function bar
in the disengaged position.
2 As the typing unit main shaft revolves, pres-
sure from the function reset bail is released
from the lower projection of the function bar.
function 3 The "spring-loaded" .. begins to
move to the front.
4 If the code combination in the typing unit
code bars is such that the tines of the function
bar are not blocked by the code bar projec-
tions, then the function bar will move far
enough forward to let the function pawl fall
into engagement.
5 As the function bar is returned to the rear
the backward movement of the reset bail, t
function pawl also is carried to the rear. I
6 The function pawl engages the function [ever
which pivots with its top portion moving to
the rear. IT IS THIS MOTION OF THE
basic operation
FUNCTION LEVER THAT INITIATES THE
OPERATION OF A FUNCTION.
7 The function pawl in its most rearward posi-
tion, still in the engaged condition, is returned
to the disengaged position by the upward
movement of the stripper blade.
8 When the function pawl is raised, its spring
pulls forward. I he function pawl's Fo-wer pro-
jection then rests on the upper rear projection
of the function bar.
CYCLE OF OPERATION illustrated Reviewed in graphic form the operation cycle is illustrated below:
A Function bar moves for-
ward . . . tines feel for
opening in code bars.
B If function bar tines
find opening, function
bar moves completely
forward . . . function
bar upper rear projec-
tion is engaged by fall-
ing function pawl.
C Function reset bail
forces function bar and
engaged pawl to rear.
Pawl engages function
lever ... function lever
initiates operation of
function.
D Stripper blade removes
pawl from function bar.
E Function mechanism
returned to disengaged
position.
Basically this cycle describes the complete
operation of the function mechanism in one
code slot. The following pages go into detail
regarding each part of the mechanism with
information as to how numerous stunt box
functions are performed.
ILI
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Function bars are literally the "passkeys"
to the performance of functions. In their
forward motion into the "lock-like" code
bars-they search for an opening.
Like keys ... function bar projections
vary ... and they vary in several ways.
The number of tines and the way they
are angled ... left, for marking and right, for spacing usually varies
from one function bar to the next.
Shown below in front views are function bars with tine arrange-
ments corresponding to the 5-level signal characters that will allow
these function bars to move completely forward.
Coding Function Bars
As indicated in this diagram ... by snap-
ping off tines, "universal" function bars
can be coded for any one of the code
characters.
components detailed
FUNCTION BARS ... how they are coded
Universal Function Bar
SUPPRESSION
4th. PULSE
1st. PULSE
5th. PULSE
2nd. PULSE
3rd. PULSE
ZERO
FIGS.-LTRS.
Illustrated above is a side view
of the fully loaded bar called the
"universal" function bar. At left,
is the front view of this bar with
tines identified as to the level of
typing unit code bars they contact.
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components detailed
FUNCTION PAWLS and LEVERS... -,A!,hat they are, what they do
Function Levers
The motion of the func-
tion levers initiates the
actual operation of a
function.
Projections of the
function lever move
slides, bails, operate
electrical contacts, block
other levers and engage
latches. Studs and bails
can be mounted on cer-
tain lever projections.
As a result of these
actions, all of the opera-
tions of the stunt box
can be performed.
Illustrated at right are
twelve function levers.
Letters identify various
projections. The purpose
of each projection is ex-
plained in the copy block
below the levers.
Function Pawls
The function pawl is
the simplest of the
principal parts of the
function mechanism.
There are three pawls
available.
Standard Pawl
Special Pawl
Accessory Pawl
A Used to operate a shift slide or an electrical contact.
B Used to operate an electrical contact which is installed in line with
the function lever and, in addition, an electrical contact installed in
line with the next lower numbered slot.
C This extension is for use in the next lower numbered slot adjacent
to the slot in which a function lever with extension "B" is used.
D Used to block the operation of the function bar in the adjacent
higher numbered slot.
E Used to block the operation of the function bar in the same slot.
F Used if the function lever is to be latched in the operated position.
G Used to operate a slide arm associated with the operation of such
functions as carriage return, line feed, horizontal tabulation, page
feed-out, etc.
I ?.._= H H __G
J This extension is similar to extension I, except that it is used whe'
spacing is not suppressed. The curve in the extension permits
operation of the function lever without operating the space suppres-
sion bail.
K This extension is required when the function lever has extension E.
A function lever with extension E can be operated only by the
release bail shaft (or by a stud in extension I or J of a function lever
in an adjacent slot). engaging the extension K.
Because stunt box applications are ever increasing, modifications of
the levers shown here and additions to the total number may occur.
The special pawl operates its own function lever
and the lever in the adjacent higher numbered
stunt box code slot.
When this special pawl is used, an accessory
pawl must be used in the higher numbered slot.
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components detailed
THE COMPLETE STUNT BOX ... additional components detailed
As illustrated, the
spring plate provides
an anchor for one end
of the function lever
spring.
Function Latches
If it is desirable to keep a function lever in the
operated position . . . a function latch is substi-
tuted for the spring plate.
In addition to providing an anchor for one end
of the function lever spring-the function latch
will engage a function lever with a latch exten-
sion, and hold the lever in the operated position
until released by the stripper blade during the
next cycle of operation.
The function lever can be kept in the latched
position for any required length of time. Three
additional methods of unlatching are available.
The first method is to have a single stud on an
adjacent lever release the latch when required.
A lever with a double stud will operate latches in
adjacent slots on both sides. A latch release bail
shaft is also available for unlatching.
Function lever latch release bail shafts span
code slots at varying intervals from 4 to 35 slots.
Shaft lengths extending across the following con-
secutive code slots are available: 4, 6, 8, 9, 12,
14, 17, 22, 25, 27, 32 and 35.
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detailed operation
FORKS, SLIDES, SWITCHES ... also ... latching... unlatching
Cutaway of Stunt Box
Three Function Mechanisms Detailed
(Note: Not in true scale.
Projections and distances are
exaggerated for greater clarity.)
0
Shift Fork
The shift fork engages the vertical posts
that move the zero, Figures-Letters
shift and suppression code bars from
the marking to the spacing position.
Shift Slide
Shift slides operate the shift fork. Shift
slides are operated by function levers.
From one to six function levers can
operate a single slide. Illustrated at
left are typical shift slides.
Switches
Switch blocks for mounting on function lever guide
plate are available. Each block can be equipped
with up to four arms for "make", "break" or
transfer contact operation. With stunt box pro-
gramming these arms can be set for momentary
operation of the contacts, for one cycle of opera-
tion, or for a sustained condition of closed or
open contacts.
A. Shows "make" or contact switch arm with rear-
ward action of top of function lever.
B. Shows "break" or no contact switch arm with
rearward action of top of function lever.
LATCHING - UNLATCHING... key to sequential selection
COLOR CODE
? FIRST FUNCTION
40 SECOND FUNCTION MECHANISM
THIRD FUNCTION MECHANISM
Let us now follow the sequential operation
of the function mechanisms in a stunt box
that has been coded to perform a function
on the receipt of the third character in a
sequence of three characters.
The first character of the three character
sequence is received by the selector, proc-
essed by the typing unit linkages and code
bars, and then interpreted by the first
function bar.
The function pawl of the selected (first)
function bar pivots the first function lever,
around its pivot point. This movement re-
moves the blocking projection of the first
function lever that has been preventing the
forward motion of the second (or adjacent)
function bar.
The first function lever is latched up in its
operated position by a latch lever. The
stripper blade rises to disengage the first
function pawl from the first function bar.
The second function bar is selected by
receipt of the second character of the select-
ing sequence, initiating a similar chain of
events.
While the second function bar is being
selected, the stripper blade descends and
strikes the first latch lever arm which
releases the first function lever. Should a
character be interposed between the first
and second character of the selecting se-
quence, the projection blocking forward
movement of the second function bar will be
restored, and will prevent selection of this
function bar by the second character of the
selecting sequence.
While the second function lever is latched
in the operated position, the third consecu-
tive character of the selecting sequence will
position the code bars to allow operation of
the third function bar, which through its
function lever activates a switch, slide,
lever, bail, etc., to perform the desired
function.
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I
 detailed op~r~ ion d For Release 2001/07/16 : CIA-RDP78SO5452A000100040010-2
SELECTIVE CALLING... terminology
Teletype Model 28 Keyboard consists of
four rows of keys; top row of "red" func-
tion keys . . . and three rows of "green"
printing character keys.
Top portion of
key top indicates
character printed
in "FIGURES."
Typical CHARACTER Key Tops
Bottom portion of
key top indicates
character printed
in "LETTERS."
Illustrated at right is a Teletype Model 28
Automatic Send-Receive Set.
Keyboard is identical to Teletype
Model 28 Page Printer.
introduction to selective calling
Before illustrating and describing a typical selec-
tive calling operation in detail, we should first be
acquainted with some general information about 2
the page printer and what it will do.
Specifically the Teletype Model 28 page printer
will perform in three basic operational areas.
I The first of these areas is referred to as
"Letters." In this condition the printer types
alphabetical characters and performs func-
tions as indicated on the lower portion of the
printer's green keytops.
When the typebox shifts to "Figures" the
second area, symbols and numerical char-
acters as indicated on the upper portion of
the keytops will be printed.
In the third area, "Select-Non Print," direct
printing is suppressed while the signal
selector and stunt box remain active. The
printer is always awake, its stunt box always
riding the line, waiting for information to be
directed to it.
The detailed description of selective calling at
right, applies to a method that one specific cus-
tomer has elected to use.
This system provides for the assignment of an
identification code to every printer on the circuit.
This code can be made up of any character or
sequence of characters.
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detailed operation
SELECTIVE CALLING ... sequential selection in action
We already know that various function levers,
pawls and bars along with other parts of the func-
tion mechanism can perform functions, block func-
tions and control time intervals of make or break
electrical contacts. With this knowledge, we can
in detail show how the systems illustrated on page
four can operate.
Identification Codes, or call directing characters
(CDC's), are assigned to each printer in the sys-
tem. The following four basic steps are in this plan:
1 Conditioning Code-With the transmission
of a sequence conditioning code such as
"Figs-H-Ltrs," the printers will respond to
the three characters in the following manner:
The "Figs" function mechanism unlatches
the "H" function mechanism. The "H"
mechanism will operate if selected. The "H"
function lever activates the latch release bail
which trips off function levers with shift
forks that return the zero and suppression
code bars from the spacing to the marking
position. This means all of the printers on
the circuit are now in what is called the
SELECT-NON PRINT condition. The "Ctrs"
signal is used to compensate for mechanical
time lag.
2 Call Directing Code-With the reception
of the identification code or call directing
character or characters (CDC's) that are
assigned to specific printers in the system
-selected stunt box function mechanisms
move the suppression code bar to the spac-
ing side, unblocking the type box clutch of
the typing unit. All of the printers that have
been selected are now in the SELECT PRINT
condition. These printers are in the "Let-
ters" print position and they are now ready
to receive and type a message.
(In calling printers, when more than one
character is used as a CDC, the function
lever of the first character is latched up to
permit the 2nd function lever to operate.
See "LATCHING ... UNLATCHING,"
page 15.)
3 End of Address-After calling in the print-
ers which are to receive a message, a
sequence of characters such as "Carriage
Return-Line Feed-Letters," is transmitted by
the originating printer. This is known as the
end of address code and causes the zero
code bars of all printers to shift to the NON-
SELECT position.
The purpose of the "END OF ADDRESS"
sequence of characters is to prevent un-
called printers from receiving the message
accidentally should their CDC be trans-
mitted during normal message traffic.
4 End of Message-After the messages have
been transmitted, it is desirable to place all
of the printers in the select-non print condi-
tion. This is accomplished by transmitting
the conditioning code, "Figs-H-Ltrs." Being
in the SELECT-NON-PRINT condition, the
printers are standing by . . . their stunt
boxes alert to line transmission.
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conclusion
OUTLOOK ... what of the future?
W'd
Teletype equipment, accepted as an important economic tool of
business and industry, serves the nation in many ways.
Military and civilian governmental agencies tie in their far flung
outposts directly to control centers for fast dissemination, evalua-
tion and disposition of information. With Teletype printed com-
munications there is no misunderstanding.
Major transportation users of Teletype equipment ... air lines,
railroads, and over-the-road carriers ... maintain schedules, han-
dle reservations, record manifests ... use Teletype units to com-
municate in every way.
Automobile manufacturers use the selective aspects of this equip-
ment to produce "custom styling" for your automobile.
Press associations use Teletype units to get news to all member
papers simultaneously.
The list is practically endless ... police, brokerage firms, hotels,
chemical manufacturers, hospitals, Red Cross, steel companies,
pipe lines, oil and gas refineries, universities, research organiza-
tions, mines ... radio, electronic and computer systems manufac-
turers . . . wholesalers, retailers, distributors in every field .. .
telephone, telegraph and cable companies . . . these and many
more, all use Teletype equipment.
The stunt box plays an important role-for these users of Teletype
products. The proven dependability and accuracy of precision
made, lab and field-tested Teletype equipment, augmented by the
versatile stunt box, assures maximum operating flexibility and
efficiency.
Every potential purchaser or lessee of communications, auto-
mation or data processing equipment should investigate thor-
oughly ... determine not only current, but consider future needs
before making an equipment choice.
Whatever the extent and complexity of the task ahead ...
Teletype Model 28 equipment is better equipped to do the job.
The acknowledged world leader in printed communications ...
equipment that bears the trademark "Teletype" ... has more
"BIG PLUS" features to offer.
Operator at keyboard
of Teletype Model 28
Send-Receive
Page Printer.
complete TELETYPE Model Jr'Iproduct t line of equipment is available
0
Model 2W
... to answer your specific questions Teletype TELETYPE CORPORATION
GENERAL OFFICES
application engineers will be pleased to help 5555 Touhy Avenue
you to most efficiently apply Model 28 units to Skokie, Illinois
Phone
Ar
C
d
312
:
ea
o
e
your ved For ReIp c ~WT~d 7 5 2A000100040010-2 TWX: 910 910-223.-223-3811
(24-hour automatic answering service)
W.U. service on premises
TEIIf A: 09451
LITERATURE
FREE
Descriptive litera-
ture concerning this
equipment is youral~
i fortheasking.Plealse?
indicate the u
,thati most intaeresL
GOVERNMENT LIAISON
OFFICE
425 13th Street, N.W.
Washington 4, D.C_
Phone: MEtropolitan 8-1016
 m.
TELETYPE
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LEADERSHIP
LINE