Kenwood KMC-18 DTMF microphone
The KMC-18 is a DTMF microphone with a lighted keypad, and is functionally equivalent to a KMC-18A in Manual Dial mode. KMC-18A is a fully programmable DTMF microphone equipped with 8 memories and 9 operating modes including Auto-Dial, Store & Send, and Last Number Redial functions. The KMC-18A can be used in either the Operating mode or Programming mode.
In the schematic for the KMC-18/A, there are four open jumpers, J1 through J4. The documentation does not indicate what these jumpers are used for.