Sony DVCAM DSR-70A Operating Instructions Manual page 58

Playback
58
Chapter 3 Recording and Playback
4
On the recorder, holding down the ENTRY/SHIFT button, press the
PREVIEW button.
Both the recorder and the player start preroll followed by playback by
the two units.
When the setup menu item 004 is set to ON and 305 set to ACCUR on
the recorder side, the recorder and player tape transports are
synchronized during the preroll allowing two-unit synchronous
playback with ±0 frame accuracy to start at the player and recorder IN
points.
To end synchronous playback while it is in progress
Press the STOP button on the recorder.