Theatre Design & Technology - Feb 1969 - 5

I have gone into the background of this development partially for a more thorough understanding of the system in its
realized form, but also to suggest to prospective system
builders alternate means of achieving comparable results.
We were spared the agony of attempting this tricky piece of
mechanical fabrication by a most fortunate appearance of a
quantity of surplus telephone and telegraph equipment. This
included, principally, punched paper tape and equipment,
both readers and perforators. It was possible with this equipment to preprogram and accurately execute up to 360 cues
per minute. Substantial modifications and additions were necessary, however, to adapt this equipment for our purposes.

Tape punch equipment group

the screens would be blacked out to give the appearance of
separate projectors. Obviously this generated a number of
alignment problems, some of which, it must be admitted,
were never fully solved. The screens themselves were of
somewhat abstract Gothic design. The advantages of the
overlap system were obvious. Not only could one image be
exchanged for another virtually instantly, but various overlay
or superimposed effects were now possible.
Hardware: Control Equipment. Various schemes were considered for programming the fairly elaborate sequencing outlined. One of the earliest was a sophisticated version of a
system used several years ago at Duquesne University: a
series of coded cards in which, for instance, on/off information would be coded in a series of holes in the lateral
dimension while the individual cues would be represented
by moving from one row of holes to the next in the longitudinal dimension. In the Duquesne system, because of the
unavailabil ity of suitable relays, the "cards" controlled power
circuits directly by having the "holes" replaced by blocks of
wood glued to long masonite strips that acted as the "card."
The rows were a half inch apart and the masonite strip was
moved just a half inch on each cue. For example, if there
happened to be a block in position No. 1 on row No.3, it
meant that on the third cue switch No.1 would be actuated,
and so on. The engineering problem in rapidly moving a
1 'x4' piece of masonite precisely a half inch was considerable and the highest speed attainable was 90 cues per
minute.
The obvious answer was to obtain a commercially built
reader of some sort, either IBM card or punched paper tape.
For some time we were frustrated in both these directions.
We began to work up a scheme combining a home-brew
reader with a rack full of relays obtained on the surplus
market. The reader was to have been a miniature version of
the Duquesne device but it no longer would have had to
actuate power control switches. Various means of achieving
this mechanically were considered, among them a system of
spring loaded fingers that would "read" all the holes in the
card at once by contact through the programmed holes in
the card to an electrified back-up plate. Progress from one
cue to the next would then be made by electrically switching from one row of sensing fingers to the next. The problem of transferring from one card to another was to be
solved by using a second reader. For example, cues No. 1-20
on the first card would be read in the first reader, then cues
41-60, and so on.

THEATRE DESIGN AND TECHNOLOGY

FEBRUARY, 1969

No where is the need to add specially built equipment to
available hardware more clearly demonstrated than in the
process of punching the tape initially. At the outset we decided to use two paper tapes in tandem. This decision was
predicated on the necessity of havi ng at least nine channels
of information to operate the various functions mentioned
earlier. Since our equipment produced tape with a maximum
of five hoi es, some means had to be found to store and
read out an additional four channels of information. The system finally devised to get information into the perforator employed 10 push buttons: one for each of the nine requisite
channels, plus one spare which was finally assigned to operate a switchboard cue light. Thus, the pre-programmed
tape signal could be integrated with the human operator of
the regular stage switchboard. Each of the push buttons was
wired to the coil of a relay that was connected in a selflatching configuration. Each relay was in parallel with one of
five solenoids on each puncher. It is important to note that
these hole solenoids did not themselves punch the tapethe energy for this was supplied by the motor. All the hole
solenoid did was to cock a mechanism that would punch a
hole in a particular position, from No. 1 to No.5, should
the punch cycle be initiated. Further, the mechanism would
stay cocked only as long as that particular solenoid was energized. (Thus the necessity for the latching relays mentioned
earlier.) This feature, however, allowed a set-up to be cleared
from the keyboard by simply opening the coil circuit of the
latching relays with another push button. The ability to erase
and rewrite a cue before printing came to be quite useful.
The punch cycle itself was initiated by a much larger solenoid on each of the punchee chassis. It engaged a very fast
acting clutch that allowed the motor to rotate the main camshaft exactly one full revolution. This happened very rapidly:
the entire cycle required less than 1/15 of a second. Since
it was found that a human operator had a great deal of difficulty getting his finger off the actuating button in a fifteenth 'of a second, a single shot relay configuration had to
be devised. This relay was opened by a cycle indicator
switch on the camshaft which operated shortly after the
punch cycle began. The single shot relay could be reset only
if the operator completely removed pressure from the "actuate" button. Thus, multiple cycling was prevented.
The operators' task was then simple enough. If he wanted
holes punched "on" for lights or projectors corresponding
to channels No. 2 and No.6, for example, he would press
the corresponding buttons. No.2 would appear as a hole in
the first position on Tabe "B" once the "Print" button had
actuated the punchers.
Several other functions were a part of the tape punch group.
One of these was the installation of pilot lamps to show the
operator which of the punch circuits had been cocked.
Related to this was a last minute addition to the system
which proved very helpful in visually checking the accuracy
of the punch set-up before actually punching the holes on
the tape. This was the "program display" which allowed the
operator to see the results of his intended program. It was
made possible by connecting the keyboard output directly to
the appropriate projector and cover flood actuator circuitry.
The punchers were also adapted to make copies of the
existing tapes either for the purpose of having back-up tapes
or for making corrections. This was accomplished by simply

Table of Contents for the Digital Edition of Theatre Design & Technology - Feb 1969