I don't know what the "LGC" means - I can picture "GC" for gain control of some sort, then "L" must be something specific to the unit or application. Instead of voltage drive, look at current through the PIN diodes. If you don't have any info about the internal structure, assume you'll have some diodes pointing in various directions, between RF ports, and to ground. On and off function is much simpler than variable attenuation control.
The easiest way to figure out the PIN arrangements is to use a curve tracer, but ohmage/dode test readings can do it too, with enough interpretation. With a CT, you'll see right away if there's significant series R that could set a voltage drive range, but I'd guess it's all diodes via RF chokes for isolation, and the currents are set up by external Rs. This is the most flexible arrangement.
Figure on needing a few tens of mA forward for ON diodes, and a few V reverse bias for OFF. Good luck.
