Page 30 - Autumn 2024

this of course could not be tolerated in a machine portion in the centre contains the printing mechanism,
which is expected to run continuously throughout the
working day. It was therefore decided to fit a thyra-
tron in the circuit.
The hole in the card is sensed at the card brush, and
causes a positive potential to be applied to the grid, the
valve now fires and discharges the 2 µF condenser
through the sorting magnet via the closed relay points,
the valve extinguishes when the condenser discharges.
The condenser is then recharged, before the next hole is
read, by means of the Condenser Charge Cam.
This arrangement has proved entirely satisfactory and
Fig. 3. Feed Mechanism of Sorter far exceeds the present requirements in that it can safely
showing card entering and card “read.” operate at 1,000 c.p.m.
Fig. 3 shows, as it were, the very heart of the machine. At the moment the machine is being mechanically
This is the sensing mechanism and it operates as re-designed to enable it to operate at this speed and
follows:- indeed we may be fast approaching the point when the
This can occur because
machine may operate too fast.
Assume first of all that the particular card passing the cards must be joggled, i.e. arranged evenly before
through the machine is not punched, the sensing brush being placed in the hopper, and if a machine was to
will not therefore complete a circuit and the card will operate at a speed much in excess of 1,000 c.p.m. it is
pass under each chute blade until finally it enters the feasible that it would empty the hopper before a new
first or reject pocket. lot of cards could be put in.
Now let us take the case of a card punched with a THE WIRE INTERPRETER
figurefour. As the card passes under the sensing brush,
commencing at Y and continuing via X, 0, 1, 2 and 3
to four it is at the same time passing under the Y, X,
0, I, 2 and 3 chute blades. When the brush senses the
hole in the card this energises the electro-magnet. This
then causes the remaining chute blades to fall down and
the card must therefore travel over the four chute blades
and thus into the four pocket.
It should be mentioned that this action is for one
column of the card only, and will he noticed that
there is a total of 80 columns. This is the arrangement
for the standard machine, but machines have been
arranged to choose a card punched with an eight digit
figure in a single run.
Fig. 5. Front view of the Wire Interpreter.
The Wire Interpreter interprets the punched holes in
a card and prints this information along the top, thus
rendering the coded information immediately available
for filing and other purposes.
Referring to the Hollerith card it will be noted that
the machine interprets alphabetical as well as numeric
information. In each column the numerals are repre-
Fig. 4. Wiring Diagram of the Sorter. sented by one punched hole, whilst the alphabetical
requires two punched holes, according to a predeter-
Fig. 4 shows the wiring diagram for the first machines mined code.
at 600 c.p.m. and, on machines built using this, trouble Fig. 5 shows the general layout of the machine with
was experienced due to arcing at the sensing brush, and the card hopper (for new cards) to the right. The raised
13
30
Become a member: https://membermojo.co.uk/ie
Become a subscriber: https://membermojo.co.uk/subscriber
Become a sponsor: https://membermojo.co.uk/sponsor
from which the cards are ejected into a container at the
left of the machine.
Fig. 8. Printing Thyratrons.
the charactor control thyratrons will therefore require
to be specially conditioned. The two grids of the valves
(2D21s) are used, one of these, of each of the 3, E, R
and + thyratrons, is connected directly to the output of
Fig. 6. Rear view of Wire Interpreter.
the Card Read Thyratron which, it may be remembered,
The card is fed into the machine face upwards and will cause the grid to go positive when a 3 is sensed at
the punched holes are sensed by twelve brushes placed the card reading brush. The other grids of the valves
in the base of the machine. The brushes are connected are under the control of sign inverters. It should of
to earth and when a hole is sensed this connects the grid course be remembered that both grids of the valve must
of the associated Card Read thyratron to "carth" and be at a positive potentia1 before it will fire.
causes it to fire; the grids are normally held at 100V Consider a card punched with a 3 only, we must then
negative. suppress everything else except the 3 and this is achieved
as follows:-
The 2nd grid of the E valve is connected to the X
Card Read Output.
The 2nd grid of the R valve is connected to the Y
Card Read Output.
Thus neither of these valves will fire since the 2nd grid
will always be maintained at 100V negative.
The 2nd grid of the + valve is maintained at 80V
negative and is connected to the output of a cathode
follower which is only fired when a 0 is sensed at the
card brushes.
The 2nd grid of the 3 valve is connected to a sign
invertor and held at a positive potential, but the invertor
will cause this to go negative if either an X, Y or an
0 is sensed.
We now have the condition that one of the grids of
Fig. 7. Card Read Thyratrons. the R, E and + valves is held negative, thus suppressing
these thyratrons, whilst both grids of the 3 valve are
The output of this
positive and it will therefore fire.
These thyratrons are used as cathode-followers and their
outputs (negative going positive) are taken to the grids valve is connected via rectifiers to the appropriate. mag-
nets of the print mechanism thus causing it to print the
of sign inverters and the character control thyratrons.
figure 3.
There are 40 character control valves, the outputs A close examination of the Hollerith Card will reveal
from which print the 26 letters of the alphabet, the that the letters and figures printed along the top are
figures 1 to 12 representing months and, in addition, two composed of dots arranged in the correct order. This
further valves for pence, i.e. 10d. and 11d. is achieved by means of 35 wires arranged in 5 rows
If we take for example the figure three it will be of seven and connected at one end to a print magnet
found to appear in the following combinations:- armature.
14