Carrier Parker SS01 slave stat - switch function

[Nanci Longley-Virgin]

I am trying to get a Carrier RTU - with old Parker electronics system running correctly and have not been able to find out what the switch on the lower right of the Slave SS01 PCB does. It has only 2 positions, but no writing on stat cover or on the board itself. I have the manual identified as VVT-2XA for this unit and nothing is identified as a switch. The red rotary switch position descriptions did not state anything needs to be done with this switch.