Audio Visual Laboratories, a long-defunct but once industry-standard maker of slide projector controls for "multi-media" and multi-image shows and corporate presentations. Based in Atlantic Highlands, NJ. Their smallest unit, Cricket, could control two Kodak Ektagraphic projectors. Then came Coyote, and Road Runner, which was a control unit only, that needed a Dove dissolve unit for each stack of three projectors. The top of the line was the Eagle II, a CP/M machine, until the Genesis, an IPM PC compatible.
Once programmed, the control signal, Positrack, could be recorded onto a audio track (usually track four) of a reel-to-reel Teac/Tascam 3440 or 34B. Signal was carried by RCA cables, and daisy chained through each Dove.
One of their simpler early products was the Acuetone, which allowed recording an advance signal for up to three Ektagraphic projectors on an audio track using tones generated and decoded by the unit. It was notable because it was used as one of the early automated methods of pushing the "go" button on lighting consoles such as the Kliegl Performance and Kliegl Performer.
More at http://en.wikipedia.org/wiki/Eagle_Computer and a tribute page (with some PDF manuals!) at http://www.honda600coupe.com/random/AVL/index.html .