Bumper Signal

Are the bumpers only using the black (ground) and the white (signal) wires?
The reason I’m asking:
I have a 12ch Remote from Ebay. It has a relay board and I was thinking of wiring the relay to the Vex I/O ports. This way I can have another remote source for the servos.
I thought I tried this before and it worked, But I can’t remember.
I was wondering if anyone else has tried this or something like it.

Yes you are correct, the Bumper Switch only uses 2 wires.