NELSON RESEARCH LABORATORIES                                 Report: NS y 79
STAFFORD                                                       Date: 21/11/57
LONDON COMPUTING SERVICE                                   Order No. NS f 6338

                           DEUCE CONTROL PANEL MANUAL
                                Miss A. Birchmore


       This report gives a description of the DEUCE Console, Reader and 
Punch and describes the function of all switches and lights. It supersedes 
Report No. NS u 241 of 11.9.57. entitled "The DEUCE Console".



2.1 	Normal Operation
2.2 	The Monitor Display
2.3 	The Output Staticiser
2.4 	The Input Dynamiciser
2.5 	Control of the Speed of the Computer
2.6 	The Go Lamp
2.7 	The TCA and TCB Lamps
2.8 	The 13 Instruction Staticiser Lamps
2.9     The Transtim and Timei keys
2.10    The External Tree Key
2.10.1	External Tree
2.10.2	Request stop
2.11    Forced Discrimination
2.12    The Clear Store key
2.13    The Alarum key
2.14    Read and Punch keys
2.15    Program Display
2.16    Drum Head Positions and Transfers

3.1 	Input/Output Medium
3.2 	The Reader
3.3 	The Punch

4.1 	Power Supply Controls
4.2 	Five Sections
4.3 	Switches
4.4 	Magnetic Drum Power Supply
4.5 	Fuses and cut-outs
4.6 	Note


     The facilities on the Control Panel, Reader and Punch may be divided into 
two classes:-

a.   Lamps and monitors which tell the operator what the computer has done, is 
doing or proposes to do.

b.   Keys, switches, buttons, lamps and dials by which the operator may control 
the computer's actions.

     These facilities may be used in normal operation. However, a good program 
will rely on manual operations as little as possible since these are time-
consuming and give scope for unrecorded errors. The facilities are intended to 
be exploited in abnormal operation, that is while testing programs and while 
servicing the computer.

     The text describes how to use each facility, and is supplemented by 
diagrams of the panels on the console and on the Reader and Punch.

     The keys on the Control Panel and on the Reader and Punch have either two 
or three positions. Where the key has an inert position this is level. Some-
times a key reverts from an active to the inert position automatically when it 
is released. Such a position will be denoted "(spring return)".

(Figure 1. Chart Explaining the Symbols Used in Later Figures).


(Figure 7. Schematic of DEUCE Control Panel).

2.1  Normal 0peration

     Since the facilities of the Control Panel are largely concerned with 
observing and modifying the normal operation of the Computer, it might be as well 
to review this normal operation with particular emphasis on those aspects which 
are specifically observed and modified.

     The DEUCE operates by carrying out a sequence of instructions. Each 
instruction (generally) specifies a transfer of information between two points in 
the machine, and also specifies the storage location of its successor. An 
instruction to be obeyed is taken into TS COUNT, which is part of Control, in some 
particular minor cycle. In the following minor cycle, called the "set-up minor 
cycle", connections are made to the selected Source, Destination and Next Instruction 
Source. In due course, transfer takes place between the selected Source and 
Destination; this transfer is operated by the application of a signal called 
"Transtim" or "TT", which is applied for an integral number of particular minor 
cycles, determined by the Wait number, the Characteristic and possibly the Timing 
number of the instruction. Eventually, the time comes for the next instruction 
to enter TS COUNT; this entry is permitted by the application of "TCI" signal for 
a single minor cycle chosen by the Timing number.

     Some instructions are "Stoppers"; these are obeyed only on external 
application of a Single-Shot impulse, either from the Control Panel or from the 
Reader or Punch; once a Single-Shot has been supplied to surmount a Stopper, 
operation proceeds normally at full speed until the next Stopper is reached.

     Certain Source and Destinations need special mention:-

Source 0 supplies information from the Reader when cards are being read and
otherwise from a row of 32 ID lamps on the Control Panel.

Destination 0 gives direct entry to TS COUNT. When D0 is selected and TT and
TCI signals are simultaneously applied, a word or words from the selected Source 
flow directly into TS COUNT.

D29 takes information from the selected Source to the output; this output is to 
rows of a card if the Punch is punching and otherwise to a row of 32 OS lamps on
the Control Panel.

D27 and D28 give discrimination facilities. Their immediate effect is to extend 
the period of TCI from one minor cycle to two if a negative number is transferred 
to D27 or a non-zero one to D28. This, in turn, effectively adds 1 to the minor 
cycle reference of the next instruction.

D24, Destination Triggers, has various functions, several of which concern us. 
The choice among these functions is determined by the Source number of the 
instruction with "24" as the Destination. There is no actual transfer of numbers 
or instructions in obeying such an instruction.

"3-24", "4-24" and "5-24" operate TCA and TCB, two circuits in the Computer which
modify the action of certain Sources and Destinations. Two lamps are provided on 
the Control Panel which are alight whenever TCA and TCB respectively are on.

"7-24" starts and "6-24" stops the Alarum on the Control Panel. The Alarum when 
on, lights a lamp and sounds a buzzer. On the Control Panel near the Alarum lamp 
is a key called "Clear Alarum"; pressing this clears the Alarum just as does 
"6-24". Raising the key kills the Alarum buzzer but leaves the Alarum lamp 
operating normally.

"12-24", "9-24", "10-24" and "2-24" are associated with the operation of the 
Reader and Punch. "12-24" is intended to start a stream of cards passing through 
the Reader. This stream of cards continues until stopped by "9-24". Similarly, 
"10-24" starts cards passing through the Punch and "9-24" stops them. "9-24" 
is used for stopping either the Reader or the Punch because they are never in 
practice run simultaneously. Of course, "12-24" can only start cards running 
through the Reader provided that there are cards in the Reader to be run. We will 
return to this point.

"2-24" is used to give a special indication of the last row of a card running 
through the Reader or Punch. A signal called TIL is provided which is present 
only for a period which covers the passage of the 12th row of a card through 
either machine. "2-24" has the effect of sending TIL signal (present or absent) 
to the discriminator circuits in Control. Thus "2-24" selects its following 
instruction from one or other of two adjacent minor cycles according to whether 
TIL signal is present or absent, that is whether or not the last row of a card 
is passing through the Reader or the Punch.

"8-24" clears the OS lamps; that is it returns all 32 lamps to the zero or off 
state. This can also be done by a key called "Clear OS" on the Control Panel.

2.2  The Monitor Display

     Two monitor tubes are used to display the contents of any part of the delay 
line store. In each case, the display takes the form of a number of horizontal 
lines of 32 green dots each, each line representing the number stored in one 
minor cycle. A "1" is represented by a bright dot, a "0" by a dim one.

     The right-hand tube has 32 such lines; it displays at one time the entire 
contents of any selected DL in minor cycle order. The selection is made by a 
rotary switch with 13 positions; 12 of these are the 12 DLs, the thirteenth 
selects TS COUNT.

     When there is a program in the high-speed store, a DL display is said to be 
in phase if the top minor cycle on the monitor is minor cycle 0 of the program. 
Every DL display has the same minor cycle at the top of the monitor, but whether 
or not the displays are in phase is a matter of chance. The display is most 
useful when brought into phase.

     A button is provided marked "mc slip" which shifts the display round by two 
minor cycles every time it is pressed. Since the construction of the monitor 
circuits is such that the top line is constrained to display an even minor cycle, 
parity can always be achieved by fifteen or less presses of the button. (Provided 
the program has an initial card to establish priority; otherwise, it may not be 
possible to get mc 0 exactly to the top.)

     The TS COUNT display should be examined only when the computer is stopped. 
It shows 32 copies of the P1, NIS, S, D, P15 and Go digits of the instruction in 
TS COUNT. The P16 and P25 digits are always zero on the display and the P(22-24) 
and P31 digits of any particular mc are alternately "1" and "0" so that they 
appear as medium-bright dots. One line of the display (that corresponding to the 
mc of entry of the instruction into TS COUNT) will show the correct wait and 
timing numbers W and T, the next line will show (W-1), (T-1) and so on, one less 
(modulo 32) each time. The line corresponding to mc 30 will have absolute wait 
and timing number, i.e. the wait number will be the number of the first mc of 
transfer and the timing number will be the mc in which the next instruction is 

     The left-hand monitor shows all TS, DS and QS all the time, by rows 
or groups of rows. From the top there are four single rows, separated by gaps, 
for TS13, TS14, TS15 and TS16 in numerical order, then three double rows for 
the DS and finally two groups of four rows each for the QS. The DS and QS 
always have an even mc at the top (in the machine sense); the QS are slipped 
round by the mc slip button in sympathy with the DLs, and finish with their mc 0 
at the top when the DLs have theirs.

     Each of the two monitors has its own "focus" and "brilliance" knob for 
use as in TV. There is a facility for splitting the DL display into blocks of 
16, 8, 4 or 2, with a gap between blocks. Setting a gap after every 8 is a 
great assistance in identifying the minor cycles. The control for this splitting 
facility is not mounted on the Control Panel.

2.3  The Output Staticiser

     Answers from the computer are normally punched on cards. A single binary 
number may instead be displayed on a row of 32 Output Staticiser lamps. A number
to be displayed on the lamps is transferred to D29 when the Punch is not 
punching. Actually, all numbers punched on cards are also displayed row by row 
on the OS lamps as they are punched, but they appear there for too short a time 
to be recognised by any but the most alert operator; the OS lamps are cleared 
immediately after the punching of each row and also at the beginning of any 
sequence of cards being punched. A Clear OS key is provided which clears the 
OS lamps each time it is pressed, and which springs back to normal when 
released. Holding the Clear OS key down is non-productive, since the OS lamps 
are cleared only once as the key is depressed and will take up the configuration 
of any further number sent to D29 whatever the static position of the Clear OS 

2.4  The Input Dynamiciser

     The Input Dynamiciser provides a means by which the operator may supply 
a single binary number for assimilation by the computer. The number set up 
appears on a row of 32 ID lamps and is then available at Source 0 for transfer 
to any selected destination. Source 0 gives the configuration on the ID lamps 
so long as the Reader is not reading cards; when the Reader is reading, the 
ID lamps are no longer effective, and Source 0 gives in turn the successive 
rows of the card being read.

     The apparatus of the ID consists of 32 ID lamps already mentioned, 32 ID 
keys, a clear ID key, 32 Special Word switches and a Special Word key. Each 
ID key works the corresponding ID lamp; pressing the key lights the lamp, raising 
the key dowses the lamp; the key springs back from either position, leaving 
the lamp on or off as the case may be. This supposes that the Clear ID key is 
in the normal horizontal position; raising or lowering the Clear ID key dowses 
all the ID lamps; the Clear ID key will lodge in its upward position but spring 
back to normal from the downward, (this is the only distinction between the 
two extreme positions). When the Clear ID key is lodged upward (or held downward), 
an ID lamp remains on only so long as its corresponding ID key is held down.

     The 32 Special Word switches provide a means of setting a standard pattern 
on the ID lamps. This standard pattern is first set on the 32 Special Word 
switches and then transferred to the ID lamps by raising or lowering the Special 
Word key. The 32 Special Word switches each have two positions, up and down; 
raising the Special Word key lights those ID lamps opposite Special Word 
switches which are down; lowering the Special Word key lights those ID lamps 
opposite the Special Word switches which are up, (this curious inversion of 
operation has no particular significance and is incorporated solely as an aid 
to memory). The Special Word key springs back to normal from either position, 
leaving on those ID lamps which have been lit (unless the Clear ID key is lodged 
upwards or held downward, in which case the ID lamps go out on releasing the 
Special Word key).

     Movement of the Special Word key does not affect those ID lamps not being 
lit by the movement; any which are already on are left on. Thus, moving the 
Special Word key up and then down lights all the ID lamps (provided the Clear ID 
key is normal).

2.5  Control of the Speed of the Computer

     Some manual control of the computer's speed is provided by three keys, the 
stop key, the single-shot key (sometimes called one-shot key) and the release 
key, and by the one-shot dial.

     The stop key can be in one of three positions - up, level or down:

a.   When "Up" (marked NORMAL), the computer goes at its own speed. If it 
     encounters a Stopper it obeys it only when it receives a one-shot.

b.   When "Level" (marked STOP), the computer interprets every instruction as
     a Stopper.

c.   When "Down" (marked AUG STOP), the computer behaves as a Stop. However,
     when a genuine stopper is reached one-shots become ineffective and stay so
     until the release key (spring return) is pressed. A warning lamp above the
     stop key is lit while one-shots are ineffective.

     Pressing down the one-shot key supplies a one-shot (spring return). Raising 
the one-shot key supplies a rapid succession of one-shots (about 600 a minute). 
The one-shot dial supplies an exact number (≤10) of one-shots (dialling 0 
supplies 10 one-shots).

     The one-shot key and one-shot dial are non-operative when Punch or Reader 
is punching or reading respectively.

2.6  The Go Lamp

     This indicates, when on, that the computer is obeying a sequence of GO 

2.7  The TCA and TCB Lamps

     The TCA (or TCB) lamp is lit when TCA (or TCB) is on.

2.8  The 13 Instruction Staticiser Lamps

     These give NIS, Source and Destination of an instruction in CONTROL if the 
computer is stopped, and are otherwise only meaningful in so far as they may 
display periodicity should the computer be continually repeating a sequence of 

2.9  The Transtim and Timei Keys

     The transtim signal, which allows transfer to take place from Source to 
Destination specified by the instruction held in TS COUNT (or by External Tree 
when this is operative) is applied (for a number of complete mc's) while the 
Transtim key (marked CONT TT) is held down.

     The TCI signal is normally applied for the one minor cycle in which Control 
is to take a new instruction, and allows an instruction to enter TS COUNT from 
the instruction highway or via destination 0. The signal is applied while the 
Timei key (marked TCI) is down. A stream of instructions enter TS COUNT, and the 
last instruction to enter TS COUNT before the key is raised stays in TS COUNT 
and is displayed on the IS lamps.

2.10  The External Tree Key

     Normally this key is level. It has two abnormal positions:

a.   While down, External Tree facility is operating.

b.   While up, Request Stop facility is operating.

2.10.1 External Tree

     This facility allows NIS, Source, Destination and Characteristic of the 
instruction in TS COUNT to be ignored and the reading from 13 IS keys (the keys 
below the Instruction Staticiser lamps) and a characteristic key (labelled Char) 
to be taken instead.

     For a correct result, it is essential that the instructions in TS COUNT 
throughout the operation should be treated as stoppers, which will usually mean 
having the stop key at STOP.

     A Normal Procedure

i)   Put Stop key at STOP

ii)  Set IS keys  ( level = 0
                  ( down  = 1
     and Char key ( up    = 0
                  ( level = 1
                  ( down  = 2

iii) Put External Tree key down

iv)  Single-shot or CONT TT

v)   Put External Tree key level. N.B. This cancels the P16 digit of the 
     instruction then in TS COUNT, changing C = 2 or 3 into C = 0 or 1.

CONT TT or Single-Shot

     If a single-shot is used, the instruction in TS COUNT will be replaced 
by its successor in the normal way, taking NIS from keys and timing number from 
instruction in TS COUNT.

     If the transtim signal is applied for a while using CONT TT key, the 
instruction in TS COUNT  will not be usurped and, provided it has not been harmed 
by the transfer, the program can continue. There are, however, certain cases 
where CONT TT key has no effect (or the wrong one): 

i)   A transfer whose length or mc is material, e.g. a transfer to D25.

ii)  A transfer to destination 24. The transtim signal does not cause trigger 
     instructions to be obeyed; these are detected and interpreted separately 
     in CONTROL.

iii) A transfer to Destination 0. For this transfer to occur the transtim 
     and TCI signals must be applied simultaneously. (This can be achieved 
     when using External Tree, with characteristic 1 and a single-shot).


     Set X, 30-0 1 on IS keys

     External Tree key down


     External Tree key level.

To Examine a Track on the Drum in the Middle of a Program

     This can be done without losing any information, including the instruction 
in TS COUNT, (except the P16 digit), so that the program can be continued afterwards.

a.   Make a note of the reading and writing head positions x and y (see 2.16).

b.   Write DL11 on to an unused track A/B thus

          0 A-31 1 using External Tree with CONT TT

          0 B-30 1   "       "      "    "    "   "

c.   Bring down track C/D to DL11 thus

          0 C-31 0 using External Tree with CONT TT 

          0 D-30 0   "       "      "    "    "   "

d.   Examine track C/D in DL11 as required.

e.   Restore DL11

          0 A-31 0 using External Tree with CONT TT

          0 B-30 0   "       "      "    "    "   "

f.   Restore reading and writing head positions x and y

          0 x-31 0 using External Tree with CONT TT

          0 y-31 1   "       "      "    "    "   "

2.10.2 Request Stop

     The Request Stop facility may be used to stop the computer on any 
instruction with particular NIS, Source or Destination or combination of these.

A Usual Procedure

i)   Stop the machine.

ii)  Make the request.

iii) Run the computer on NORMAL or at STOP with single-shots, until Request 
     Stop operates. (These single-shots may be supplied by Punch or Reader, 
     but if a Request Stop succeeds during punching or reading, Punch and
     Reader will not be cleared. Further, having the External Tree key 
     raised makes the Reader "not ready", so the Initial Input key and Request 
     Stop cannot be used simultaneously.)

iv)  Put key at STOP if it is not already there.

v)   Remove a Request Stop condition (a or b or c below).

How to make the Request

i)   Raise External Tree key.

ii)  Set the three Request Stop switches. They correspond in natural order to 
     NIS, Source and Destination; the computer examines those of the NIS, 
     Source and Destination of the instruction in CONTROL for which the 
     corresponding Request stop switch is down.

iii) Set the NIS, Source and/or Destination at which the stop was requested on 
     the IS keys. (The position of the characteristic key does not affect 
     Request Stop.)

Where the stop comes

     The computer continues normally (full speed or single-shotting) until there 
is complete agreement between the part of the current instruction selected by 
the Request Stop switches and the reading on the corresponding IS keys; it then 
stops (however, the GO lamp will be on).

     For example, suppose the External Tree key is up and 7 13-28 is set on the 
IS keys, then

a)   if all Request Stop switches are down the computer stops when an instruction
     7 13-28 is encountered;

b)   if only Source and Destination Request Stop switches are down the computer
     stops at the first 13-28 instruction it encounters, regardless of NIS.

     This example demonstrates that the Request Stop facility is made more 
selective by having more switches down.

Nature of the Stop

     The instruction stopped by request is repeatedly inhibited to prevent 
transfer, and taking of the next instruction into TS COUNT. Request Stop should 
not be used on Destination 24 instructions; or on 17-0 or 18-0 instructions on 
machines with Automatic Instruction Modification. The reason in both cases is 
that the action called for will occur repeatedly until Request Stop is released; 
e.g. Request Stop on 0-24 would cause repeated multiplications and on 17-0 
would cause repeated modification in QS17.

How to Reach the next Instruction

     To go beyond this instruction, a condition of the Request Stop must be 
removed, i.e,
     a) External Tree key no longer raised, or
     b) all Request Stop switches up, or possibly an extra switch down, or
     c) one of the relevant IS keys altered.

     This is best done with the machine at stop. Then on release by a) or b) 
or c) above, this instruction is obeyed and the next instruction is treated like 
a Stopper.

     a) implies that it is not possible to use External Tree to alter the 
instruction for which the stop has been requested. However, it is not too late to 
force a discrimination using the Discrim key, or a TIL instruction using the TIL 

2.11 Forced Discrimination

     While the key marked TIL is in its lowered position, the TIL signal is 
given continuously.

     The discrimination key (marked DISCRIM) has three positions:-

i)   Level (marked N0RMAL). Instructions with destination 27 or 28 are obeyed 

ii)  Down (marked ON). After an instruction with D27 or D28 the next instruction 
     is chosen as if a negative number had been transferred to D27, or a 
     nonzero number to D28.

iii) Up (marked OFF). After instructions with D27 or D28, the next instruction 
     is chosen as if a positive number had been transferred to D27 or a zero 
     number to D28.

2.12 The Clear Store Key

     Pulling and pressing the Clear Store key (spring return) clears the high-
speed store (but not the drum).

2.13 The Alarum Key

     When the Alarum is stimmed by a 7-24 instruction, a buzzer sounds and a 
red lamp on the Control Panel is lit.

     To clear Alarum press down the Alarum key (spring position).

     To suppress buzzer, raise the Alarum key.

2.14 Read and Punch Keys

     There are three keys on the Control Panel which allow Read and Punch to 
be called or cleared manually, instead of by the DEUCE trigger instructions 
12-24, 10-24, 9-24. They are labelled Read, Single Read and Punch.

     To call Read, press down the Read key. To clear Read, raise the Read key. 
To Read a single card, press down the Single Read key.

     To call Punch, press down the Punch key. To clear Punch, raise the Punch 

     A lamp above the Read key is lit while Read is called, and a corresponding 
lamp above the Punch key is lit when Punch is called.

2.15 Program Display

     This facility enables the operator to punch, on successive rows of cards, 
binary instructions in the order which they are being obeyed.

To Use It

i)   Stop the computer when the program has reached a point just before the 
     sequence to be displayed.

ii)  Set the stop key at AUG STOP.

iii) Run Program Display cards into the Punch.

iv)  Push down Program Display key (the lamp above the key will be lit until 
     Program Display is cleared).

v)   The punching continues until:

     a)  a stopper is reached; in this case Program Display is automatically
         cleared. Since the STOP key is at AUG STOP single-shots become
         ineffective. To continue Program Display press first Release key and
         then Program Display key.

  or b)  Program Display is cleared by raising the Program Display key.

  or c)  Punch is cleared (manually or by a 9-24 instruction). To continue,
         call Punch using the Punch key on the Control Panel.

  or d)  Punch is not Ready because it has run out of cards or because the
         Stop key on the Punch has been pressed. To continue, put cards in
         Punch hopper and run in.

What to expect on the Program Display Cards

     The instruction in TS COUNT is obeyed when the one-shot from a row of a 
card running through the Punch arrives. The next instruction enters TS COUNT 
and is also sent to Destination 29 and so is punched on this row. This means

i)   the instruction in TS COUNT, when Program Display is stimmed, is not 
     recorded, and the next instruction is the first instruction punched;

ii)  when Program Display stops, the last instruction punched on the cards, 
     that is the instruction in TS COUNT, has not yet been obeyed;

iii) successive instructions are normally punched on successive rows, although 
     sometimes during a magnetic sequence a row is left blank where its one-shot 
     was ineffective due to Control-Magnetics Interlock.

Read and Punch Sequences

     To display a sequence including reading instructions, it is necessary 
both to stop cards running through the Reader, since the one-shots from them 
would cause confusion, and also to simulate the rows of the input cards on the 
ID lamps.

     A punching sequence can be displayed; the output is lost.

Request Stop

     A Request Stop may be made during Program Display, but the Punch will not 
be automatically cleared when the Request stop has been reached, so cards, blank 
in the DEUCE field, will be punched until they are stopped by the operator.

2.16 Drum Head Positions and Transfers

(Figure 6. Lamps Associated with Drum Transfers).

     There are two sets of lamps which give the Reading and Writing head 
positions and another set which give the source and characteristic of the last 
instruction which effected a transfer between drum and high-speed store. These 
can be seen inside the cabinet near the drum. (In some DEUCEs these are 
duplicated on the Control Panel.)

     The Reading and Writing head positions are displayed in binary on two 
vertical sets of four lamps, labelled Read Track number and Write Track number. 
The least significant figure is at the bottom.

     The Source number of the last drum transfer is similarly displayed on 
lamps labelled Head Number; there are also two lamps, one of which is lit if 
c = 0 (labelled Read) and the other if c = 1 (labelled Write) in the last 
magnetic transfer position obeyed. 


3.1 Input/Output Medium

     The DEUCE communicates with the outside world by means of standard 80-
column Hollerith Punched cards. All DEUCEs can use 32 of the 80 columns directly,
and some DEUCEs can also use 64 of the 80 columns directly, the choice being
made by a two-position switch on the appropriate Hollerith machine. When only
32 columns are used, these are columns 21-52, and when 64 columns are used, these
are columns 17-80.

3.2 The Reader

(Figure 2. Lamp and Key Panel on the Hollerith Reader).

     Cards to be read are placed in the hopper of the Reader; they pass
through the mechanism and emerge in the stacker. If the machine is stationary,
there are positions for four cards between the first card in the hopper and the
last card in the stacker. These positions are numbered 2, 3, 4 and 5, the first
card position in the hopper being number 1 and the last card in the stacker
number 6. A unit operation of the Reader (the least it can do), called a "Card
Cycle", is the movement forward by one position of every card in the machine.
If there were previously a card in position 3, it moves into position 4, and it
is during this movement that the card is read, by "brushes" in the Reader.

     The movement of cards is actually more complicated than this; they do
not necessarily all move at once. There are two parts, the lower movement which
moves cards from positions 4 to 5 and 5 to 6, and the upper movement which moves
cards from positions 1 to 2, 2 to 3 and 3 to 4. The upper movement is driven
from the lower movement by a clutch; thus the upper movement can never operate
without the lower movement.

     On starting the Reader from still, both movements start simultaneously.
When it is decided to stop the Reader, the upper movement stops at the end of
the current card cycle. This freezes the cards at that time in positions 1, 2 and
3. The lower movement continues for just another two cycles, so that the cards
from positions 4 and 5 are decanted into the stacker.

     It is possible, in circumstances that are about to be explained, for cards
to pass through the Reader without their contents being made available to the
DEUCE on the Input Dynamiciser. There are thus three types of card cycle, a
genuine Reading Cycle, a Feeding Cycle and a cycle in which only the lower drive
is operating. This last type of cycle occurs only as a postscript to a sequence
of one or more reading or feeding cycles.

     There are three keys on the Reader called respectively Initial Input, Run
Out and Run In; each operates by being pressed downward from its normal hori-
zontal position. The Run In key also operates when pressed upwards, but this
time with a different effect, that of stopping the Reader whatever it is doing.
The action of the Reader will be illustrated by a few examples.

     Suppose first that the DEUCE is doing a program in which it will shortly
require to read in certain information from cards. These cards are placed in
the hopper and the Run In key pressed. The Reader does two Feeding Cycles which
bring the front card from the hopper into position 3. At this point, a relay
called Q comes on in the Reader which indicates that there is a card ready to be
read. (Relay Q also lights an indicating "Ready" lamp on the Reader.) In due
course the program reaches the point where the information is required and obeys
the Instruction "12-24" which stimulates Trigger READ. The fact that both
Trigger READ and Relay Q are on, causes Reading Cycles to start, and the cards
from the hopper pass successively from position 3 to 4 past the Reading Brushes.
As the first Reading Cycle starts, the Source 0 connections are removed from the
row of 32 Input Dynamiciser lamps on the Control Panel and connected instead to
the Reading Brushes. Then:- 

i)   for 32 column reading these connections are such that Source 0 gives the
     configurations on columns 21-52 of successive rows as they pass the

ii)  for 64 column reading, these connections are such that Source 0 gives
     first the configurations on columns 17-48 and, when this has been taken
     from Source 0, the configurations on columns 49-80 of successive rows as
     they pass the brushes.

     As each row of each card comes into position under the brushes, the Reader
gives a one-shot signal. For a period covering the passage of the twelfth (last)
row of each card under the brushes a signal called TIL (Twelfth Impulse Line)
is given; its presence can be detected by the instruction 2-24, in an analagous
way to the detection of a negative number by D27 or a non-zero number by D28.
During reading cycles, the one-shot key and dial on the Main Control Panel are

     When all the information required has been assimilated, the instruction
"9-24" is obeyed which clears Trigger READ. This may happen in the middle of a
card, but from that moment there are no further one-shot or TIL signals, and the
Source 0 connections revert to the ID lamps on the Control Panel. At the end
of the current card cycle, the upper movement stops, but the lower movement
continues for a further two cycles.

     The effect would have been the same if Trigger READ had been stimulated
first and the cards run in afterwards. Instructions of the form "0-D" which
read from a row of a card, or from the left-hand side of the row in the case of
64 column Read, to any Destination D are made Stoppers; they are not obeyed
until the row comes along, however long they wait. Pressing the Run In key gives
two feeding cycles at the end of which Relay Q comes on. Since Trigger READ
is already on, the first reading cycle starts immediately, following right on
from the second feeding cycle.

     Relay Q may be cleared at any time by raising the Run In key and then
returning it to normal. Reading cycles cannot now take place, even if Trigger
READ is stimulated, in spite of the fact that a card may be present in position
3. If Relay Q is cleared during the process of reading, the current reading
cycle is completed before the upper clutch disengages and stops the upper drive.

     The Run In key is usually pressed when there is a card in position 1
(i.e. in the hopper), but no card in positions 2 and 3. In this case, two
feeding cycles take place, bringing the card from position 1 to position 3, and
the Q relay comes on. This action is modified by the presence originally of a
card in position 2 or in position 3; in the former case there is only one
feeding cycle, after which Relay Q comes on; in the latter case, no feeding
cycles at all, merely the stimulation of Relay Q if it were previously off.

     Pressing the Run Out key is effective only if the upper drive is station-
ary. In this case it initiates a sequence of feeding cycles which continue
until position 3 is empty. If there were previously cards in the hopper and
positions 2 and 3, this has the effect of running them all out into the stacker,
since the lower drive always does two cycles on its own after the upper drive
has stopped.

     The Initial Input key is used for reading in a new program from scratch.
It has three immediate effects; it sends two signals to the DEUCE which respec-
tively clear the whole Delay Line store and stimulate Trigger READ and it also
imitates the action of the Run In key.

     The Initial Input key becomes completely ineffective if certain Control
Panel keys are standing in abnormal positions. A "Not Ready" lamp on the Reader
indicates this situation. It will be appreciated that the "Ready" and "Not
Ready" lamps on the Reader may well be alight at the same time, since the former
refers only to the state of the Reader, the latter only to that of the Main
Control Panel.

     Lamps are provided on the Reader to indicate when Running In, Running Out
and Reading are in progress (the last one flashing once for each Reading Cycle)
and when Read has been called either by "12-24" or by the Read key on the Control

     There is a point of time towards the end of each card cycle after which
the instruction "9-24" will be too late to stop the upper movement at the end of
the current reading cycle. As a result, a further card will pass through the
reading position but will not be read at all. If this happens, a lamp called
"Missed Card" comes on, and the "Ready" lamp goes off. This position can be
reversed only by first raising and then pressing the "Run In" key. Until this
is done the Reader is quite inoperative.

     Six "Card Position" lamps are provided to indicate the presence of cards
in the hopper, the stacker and each of the four internal card positions.

     Trigger READ is cleared immediately by any hole punched in column 54 which
passes the Reading Brushes during a reading cycle. The Single-Shot Signal for
this row occurs, but no subsequent ones.

3.3 The Punch

(Figure 3. Lamp and Key Panel on the Hollerith Punch).

(Figure 4. Switch Panel on the Hollerith Punch).

     The action of the Punch is very similar to that of the Reader. It will be
described largely by references to the differences between the two.

     On starting a sequence of Punching Cycles, the Destination 29 connections
to the row of 32 OC lamps on the Control Panel are switched so that the success-
ive configurations there are also punched on successive rows (2 per row if using
64 column Punch) of a card passing through the Punch. After each row, a signal
is sent from the Punch which clears the OS. This saves the need to clear the OS
by an instruction before setting up the configuration for each successive row,
but not between setting the L.H.S. and R.H.S. configurations when using 64 Column
Punch; to cope with the first row of a sequence of cards, calling punch by the
instruction "10-24" is also arranged to clear the OS. These remarks apply only
to Punching Cycles; as in the case of the Reader, Feeding Cycles may take place
in which there is no connection with the rest of the DEUCE.

     In the Punch, there is only one internal card position before the punching
station. This gives 5 card positions altogether, position 1 being the first card
in the hopper, position 2 coming before the Punching station, positions 3 and 4
afterwards, and position 5 being the last card in the stacker. When a set of
punching is complete, the last card punched remains in position 3. A Run Out key
is therefore provided which causes two feeding cycles and brings this card out
into the stacker. There is also a Run In key (which in this case need never give
more than one feeding cycle) and a separate Stop key.

     As well as the 32 (or 64) columns of information from the DEUCE, twelve more
columns of reference numbers are also punched on each card. An 8-digit group of
fixed parameters is punched on columns 5 to 12; these are set up on 8 rotary
switches before the start of the run. A 4-digit card number is punched on columns
13-16; this card number steps on by one automatically for each card. The card
number to be punched on the first card of the run is set up on a set of 4 rotary
switches, these four switches are automatically returned to zero by pressing a
"Clear" key.

(Figure 5. Counter Switch and Parameter Switch - I presume this belongs here).

     All the numbering can be suppressed by depressing a key to the left of the
"Clear" key.

     On Run out the card numbering is inoperative; thus on the next punching
run there will be 2 unnumbered cards at the front, if cards were in the stacker
on Run out. 


4.1 Power Supply Controls

     The main power supply to the computer comes through the Power Unit which
is supplied with 3-phase mains.

     The power supply controls and indicating lamps are duplicated; there is
one set of controls on the front of the Power Unit and a parallel set on the
Main Control Panel at the top of the right-hand section. The set of controls on
the Control Panel is not quite complete, but is sufficient for all normal and
most abnormal circumstances.

4.2 Five Sections.

     The power supply may be regarded as split into five sections:-

A.   Delay line thermostats and certain indicating lamps which must be on at
     all times.

B.   Fans for forced air cooling system, if any.

C.   Valve heaters.

D.   All H.T. Supplies except the supply to the solenoids which control the
     punching in the output cards.

E.   H.T. supply to the solenoids which control the punching in the output

4.3 Switches

     Section A has no switch; the supply is on unless the whole mains supply
to the computer is removed.

     Sections B, C, D and E are controlled by four separate switches which are
duplicated on the Power Unit and the Main Control Panel. Each switch consists
of two lamps, one red and one green, and two push buttons, one for off and one
for on. One of the two lamps should always be lit, the red one if the particular
section is off, the green one if it is on. The "on" button is pressed to put
the section on, the "off" button to put it off. In two of the four cases, the
"off" button is labelled "off and reset" to indicate that it has a second
auxiliary function which will be described below.

     The four switches are interlocked in a chain; C cannot be on if B is off,
or D if C is off, or E if D is off. Thus if all four are off, they can be put
on only in the order B, C, D, E. If all are on, all are automatically put off by
pressing the B "off" button, or (say) D and E are put off by pressing the D
"off" button. However, it is generally considered preferable to put them off
separately in the order E, D, C, B.

     There is an additional time interlock between C and D on switching on;
if C is off and is put on, the D "on" button is temporarily ineffective and can
be used to put section D on only after a delay of about one minute. There is
no similar provision on switching off.

4.4 Magnetic Drum Power Supply

     Switching on and off is controlled by the four pairs of push buttons
described, except that it is also necessary to switch the magnetic drum power
supply by the toggle switch on the chassis below the drum. This should be
switched off before or after switching off the main power supply,  and should
be switched on after switching on the main supply. The drum will take some
time to come into synchronisation; while it is doing so, the "sync alarum"
will operate intermittently; attempts should be made to clear this by pressing
the (spring) key below it until the Alarum remains off on releasing the key.
This indicates that the drum is now in synchronism. (On later machines the
"sync alarum" control key operates slightly differently.)

4.5 Fuses and Cut-outs

     The circuits of the computer are protected by a number of fuses and overload
cut-outs; if a fuse blows or a cut-out operates, some or all mains supply
sections will go off and cannot be put on again by the normal procedure described
above. If this happens, the operator should inform the engineer and leave the

     However, in the absence of an engineer there are certain limited actions
which the operator may take to rectify some types of failure; these are concerned
with the operation of twelve overload cut-outs, ten for various sections of
the H.T. supply, one for the heater supply and one for the mains supply. If any
of these operates, all or some of the mains supply sections go off and a red lamp
is lit on the Power Unit and the main Control Panel indicating which particular
cut-out has operated. The cut-out may be reset by pressing a button; for any
of the ten H.T. cut-outs, this button is the "H.T. off" button; for the heater
cut-out it is the "Heater off" button; for the mains cut-out it is the "Mains
Fuse Reset" button on the Power Unit which is not duplicated on the Main Control

     If one of these twelve cut-outs operates, the computer may be restarted
by first pressing the appropriate reset button and then restoring the mains supply
sections in the normal way. However, two points should be noted:

a.   the computer may be left in a faulty condition after the cut-out is reset;
	 its operation should be checked before resuming work;

b.   if the cut-out again operates immediately, NO FURTHER ATTEMPT should be
     made; computer operation must be suspended until an engineer is available
     to rectify the fault.

4.6 Note

     If a card jams in the Reader or Punch, a normal procedure is to clear the
jam without switching off the computer, so that work may be resumed without losing
the current intermediate results in store. It should be realised that the large
switches on the Reader and Punch control only the supply to the motor drive and
to most of the indicating lamps; the H.T. supplies are still present, so that
care should be taken. The H.T. supply to the punching solenoids may be removed
by the "Hollerith off" button on the Main Control Panel or Power Unit, but this
is of only marginal assistance. 

                                                         signed: A Birchmore
                                                    LONDON COMPUTING SERVICE
                                                       N.R.L., MARCONI HOUSE