Tektronix 1A2 Technical Instructions page 14

2-7
a channel is turned off (its shunt diodes are on), current is supplied
to the paraphase amplifier of that channel from the switching multi-
vibrator through the shunt diodes.
The switching multi, which is bistable in all modes, is controlled by
the MODE sw and the trigger BO. Since the voltage swing at the emitters
of the hybrid amplifier is small (it is current driven), the required
voltage swing at the multi output is correspondingly small.
In the ALT and CHOP modes, the multi's switching rate is determined by
the trigger BO. In the ALT mode, the BO receives a signal at the end
of each sweep which causes it to send a trigger to the multi. With a
547 whose HORIZONTAL DISPLAY is set to A ALT B, triggers are sent to
the BO and to the multi which lock Channel 1 to time base A and Channel
2 to time base B.
In the CHOP mode of operation, the BO free runs to send triggers to
the multi at a 440 KC rate. The multi divides by 2 to provide a
220 KC chopping rate. The BO also provides blanking pulses in the
CHOP mode.