TELECOMMUNICATIONS OFF-HOOK AND INTRUSION DETECTION METHOD AND APPARATUS

摘要

A method and apparatus to detect off-hook and intrusion conditions on a telephone line. A voltage to frequency converter is used to convert the voltage measured between the TIP and RING terminals of a telephone line to a frequency. The voltage is continuously monitored, once during each sample period. T he measured frequency is compared to predetermined threshold values to determin e the state of the telephone line. The predetermined threshold values are updated in each sample period.