Patent ID: 6104791
Filing Date: 2000-08-15
Classification: H04M

Abstract:
A method for monitoring changes in a line voltage transmitted through a telephone line from a central office to detect when particular events occur on a telephone line in order to control the operation of a modem connected to the telephone line, comprising the steps of:receiving the line voltage appearing in the telephone line in a voltage sensor;sensing changes in the line voltage indicative of the occurrence of a particular telephone line event;outputting an activation signal when a line voltage change of a predetermined value is sensed;operating a loop current switch with the activation signal to control a flow of current through the loop current switch to an isolation device;controlling the activation of the isolation device in response to the current flowing through the loop current switch, andtransmitting an output signal to a microcontroller device in the modem in response to a change in state of the isolation device to alert the microcontroller device that the particular telephone line condition has occurred.