Quick reference
SE-> Single Ended SCSI
HVD-> High Voltage Differential
LVD-> Low Voltage Differential
The voltage between the DIFFSENSE pin (#16) and Ground Pin (pin 50) can give an idea about the SCSI type from the SCSI peripheral under test. In a 68 pin SCSI Female connector, Pin # 16 is DIFFSENSE ( in HVD and LVD/MSE devices, whereas it is ground in SE devices)
For differentiating between devices :-
measure voltage between pin #50 (GND) and pin # 16
If voltage > 2.4 volts, then it is HVD.
If voltage < 0.5 V, it is SE
If 0.7 v < voltage < 1.9 v, it is LVD/MSE
The 50 pin Amphenol Male connector (centronics type) has pin #11 as Diffsense and Pin #16 as ground. (for M4 9 track drives round-reel)