Sony DFS-700 Operating Instructions Manual page 121

Timing of the trigger (T1/T2) signals
Player A
Player B
Recorder
T1
T2
PGM OUT
signal
The timing of the trigger signals output by the BVE-600 is as follows.
VCRs start IN point Effect start point
Background bus image
Preroll
A-roll period
Timing of trigger signals in A/B roll editing
OUT point VCRs stop
Foreground bus image
Effect
Postroll
execution
(transition)
B-roll period
Chapter 5 Control From Editing Control Units
5-7