In 1965 while I was in the Drama School at Yale, Dennis Carnine and I designed a unique analogue punch card theater lighting control system. Thyratron and saturable reactor dimmer systems had been developed by George Izenour and signaled the advent of electronic lighting control in the theater. Magnetic amplifiers briefly had their day but were replaced by silicon controlled rectifiers. The possibilities for using punch cards were soon explored but computer controlled lighting systems were prohibitively expensive for any but the largest theaters.
Typical electronic systems at the time utilized binary code on standard punch cards to record scene presets. These systems were costly because digital to analog converters were required to drive the remote dimmers in response to the recorded values. Digital technology offered great flexibility and operator convenience but the cost was high in those days and the card processing equipment was more suited to commercial requirements than to small organizations.
To cut costs and make electronic lighting control systems within the reach of regional and small repertory theaters and at a fraction of the cost of digital controlled systems, Dennis Carnine and I invented an analog punch card lighting control system as part of our Master's Thesis work.What was unusual about our system was that there was a single punch hole in each column on the card, rather than a binary code made up of multiple holes. (Each punch card stored the dimmer presets for a particular point in the show. One column on each punch card was devoted to a particular dimmer.) The position of this hole could vary over a four inch height from near the bottom of the card to the top. That analogue position corresponded to the intensity of the corresponding dimmer from off to full on. A beam of light passing through that hole onto a printed array of photosensitive potentiometers could directly contol an electronic dimmer without the need for costly digital to analog converters.
Here are photos of a few parts I designed and built for our prototype analogue lighting control system: