These remotes can be configured as either Tone or DC signalling depending on the option board installed in them. Yes, there are 31 posts for connections on the bottom, including Line +/-, external speaker, microphone, Line Operated Transmit Light, various connections for MODEN paging encoders, recording equipment, etc.
If I recall correctly, it's one or the other (Tone or DC), but not both. Depending on the configuration of the unit it will control either a single base station/repeater, or multiple base stations/repeaters. I believe the multi-base unit had a big amphenol connector coming out of it that terminated into a punch down block for connection to the base stations. THAT unit might have been able to do both Tone and DC, but I don't have manuals for that unit (that I know of), only the single-base unit.
If you look in the unit and see a board towards the rear of the remote with a tone reed on it, then it's a tone signalling unit. If it just has a board with some transformers on it, it's DC. I have the manual for these units and will check tomorrow on the part numbers and more definitive information on how to tell whats what