Keysight Truevolt Serie Mode D'emploi page 459

SCPI Programming Reference
VM Comp Output (BNC)
The rear-panel VM Comp (voltmeter complete) output provides a 3.3 V pulse after each measurement
completion to implement a standard hardware handshake sequence between measurement and switch-
ing devices.
The signal shown is for a negative pulse.
460 Keysight Truevolt Series Operating and Service Guide