Hitachi HV-F31CL Operation Manual page 51

3) Flash signal output
low 0 Vdc, high 5 Vdc
4) Serial communication (RS-232C)
RXD to camera
TXD to PC
5) Power supply input
12 V rated
(Stable operation at 10.5 to 15 VDC (neither ripple nor noise))
3. External trigger input (TRIG IN connector)
low 0 Vdc, high 2 to 5 Vdc
NOTE 1
Both external HD/VD input and serial communication are not available
at the same time. See page 9.
NOTE 2
Only one input is available for external trigger among Camera Link, DC
IN/SYNC and TRIG IN.
Set unused trigger inputs to be open or Low (GND) level.
37
(see NOTE 1)
low: -3 to -15V, high: 3 to15V
low: -5 to -9V, high: 5 to 9V
(see NOTE 2)