Patent ID: 7515672

Claim:
A communication system, comprising: phone line side circuitry configured for coupling to phone lines; powered side circuitry configured for coupling to the phone line side circuitry through an isolation barrier comprised of a plurality of isolation elements; and a DC holding circuit within the phone line side circuitry, the DC holding circuit being programmable in response to data transmitted across the isolation barrier to operate the DC holding circuit in a plurality of modes, the DC holding circuit operates in at least a first mode to meet a first phone line interface standard and a second mode to meet a second phone line interface standard, the second phone line interface standard having a DC current limit requirement; wherein the powered side circuitry is configured to communicate a first digital differential signal to at least two of the plurality of isolation elements, the at least two isolation elements comprising at least a first isolation capacitor and a second isolation capacitor; wherein the phone line side circuitry is configured to communicate a second digital differential signal to the first isolation capacitor and the second isolation capacitor so that the first and second digital differential signals are communicated across the same first and second isolation capacitors and so that the first and second isolation capacitors bidirectionally transfer the first and second digital differential signals; wherein the powered side circuitry is further configured to provide a clock signal to the phone line side circuitry through at least one of the plurality of isolation elements; and wherein the powered side circuitry and the phone line side circuitry are configured so that power is provided from the powered side circuitry to the phone line side circuitry while still maintaining the isolation required by the phone line isolation regulatory standards.