The inter-switch interconnect system functions to interface a packet switch with a legacy Time Division Multiplexed switch without requiring any changes to the Time Division Multiplexed switch. The inter-switch interconnect system implements a packet-based call connection system that is triggered by the standard CCS7-ISUP signaling protocol, where the packet-capable Time Division Multiplexed switch controls the set-up and tear-down of the packet connections through the Asynchronous Transfer Mode network to the non-packet-capable Time Division Multiplexed switch using the standard CCS7-ISUP signaling protocol for both incoming and outgoing calls. The packet-capable Time Division Multiplexed switch controls call connections both to and from the legacy non-packet-capable Time Division Multiplexed switch.