The 961 Sequencer Interface consists of two multi-channel V-Trigger to S-Trigger converters, two S-Trigger to V-Trigger converters, and an audio to V-Trigger converter. A V-Trigger is a voltage trigger which is like a positive voltage Gate pulse. An S-Trigger is an active low "short" to ground signal which can be wired-or'd.
The V-Trigger to S-Trigger consists of six A inputs and six B inputs. The A inputs are level sensitive so the S-Trigger output is the same duration as the V-Trigger inputs. The B inputs are edge sensitive and drive a variable one-shot (using a unijunction transistor) so the S-Trigger output can be varied from 50 mS to 4 seconds.
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