RTS Model SSA-324 is a System to System Adapter or interface. It interconnects the voice signals between different intercom systems. In addition, it can optionally interconnect calls or tally signals between systems. Each SSA-324 includes two (2) 2-wire to 4-wire converters. The 4-wire interface can deliver and accept high level signals. An SSA-324 can also function as a 2-wire to 2-wire interface by interconnecting the two (2) individual interfaces at the 4-wire level. The SSA-324 does two (2) voice channels when used as a dual 2-wire to 4-wire interface, and one (1) voice channel when functioning as a 2-wire to 2-wire interface.