The RTS trunking system manages intercommunications between separate intercom systems using intercom ports that have been reserved and interconnected between the intercom systems. Keypanels or other data devices can then communicate with various destinations in other intercom systems via the reserved intercom ports. (This is different from bus expansion, in which the bus systems of two or more frames are interconnected to form one system with decentralized hardware.)

The RTS trunking system consists of an RTS model TM-2000/MTM-2000 and one or more RTS model ICP-2000 interconnection panels, depending on the number of intercom systems to be trunked. A backup TM-2000/MTM-2000 may also be added to prevent downtime in the event of a failure of the main master control unit. When both main and backup control units are used, an RTS model SWP-2000 switch over panel is required.