LINE CURRENT PROTECTION CIRCUIT AND METHOD FOR LINEAR AND NONLINEAR HOLD CIRCUIT

摘要

A novel line-current protection circuit (44) for detecting excessive line current (42) from a telephone line and protecting line interface circuitry from the excessive line current (42) is presented. The protection circuit (44) is adapted to detect when an excessive current is present on the tip (32) and ring (34) lines indicative of the misconnection of the modem or other line interface device with a telephone network that presents an incompatible interface standard. The preferred embodiment appreciates the multimode hold current specifications throughout the world and evaluates the connection of the line interface circuit (38) with a telephone line to determine the compatibility therewith. When excessive line current (42) is detected, the line-protection circuit (44) switches the vulnerable line interface out of the circuit. When compatible line current levels are detected, the present invention reconfigures the configurable hold circuit (66) into its original operating (e.g., non-testing) state for call processing.