I'm sure this is a simple thing but I am having difficulty in understanding how to interpret the 125VDC voltage readings for Mark 5 switch inputs at the terminals of a DTBB board. I am troubleshooting about 5 alarms that are related to input devices landing on the CD core termination board DTBB. I am trying to isolate the problem to either Mark V hardware or real world devices. Referencing the GEH-6195 Application Manual Appendix D - Signal Flow diagrams page D-4 (Digital Inputs on DTBB Terminal Board), I am trying to determine how to measure VDC with a DMM the contact inputs in a way as to know whether they are closed or open. I would like to know what to expect to see in VDC across the POS and the RET input terminals when the contacts are closed and/or open. Also I would like to know what to expect to see referencing ground with the black lead of the DMM and the red lead at the POS and subsequently the RET terminals for both the closed and open states of a contact. Thank you for your help and your patience.