Expandable local inter-system bus architecture in a multiplexed environment

In an communication system including a computer system comprising a digital signal processing adapter for performing a set of tasks, and a E-1 port for providing and receiving time division multiplexed (TDM) signals in accordance with a first inter-system communication protocol, such as the E-1 or T-1 protocols, a communication subsystem, for coupling to the IP system. The communication subsystem includes an E-1 link for coupling to the first I/O port, and for providing and receiving TDM signals in accordance with the E-1 or T-1 protocols. The subsystem further includes a digital signal processor adapter, coupled to the second I/O port, for enhancing processing capability of the digital signal processing resource; and a third I/O port, coupled to the digital signal processor circuit, for providing and receiving signals in accordance with the first or a second inter-system communication protocol.