WIRE BROADCASTING ADAPTOR FOR SHARED WIRE BROADCASTING EXCHANGE SYSTEM

摘要

PURPOSE:To control the terminals of shared lines by means of two lines the same as a single line requiring no earth line by using a standard telephone set by providing the adaptor with a called party part for generating a false bell signal based upon voltage impressed to a line and a caller part for injecting a calling tone to the reference telephone set and guaranteeing the voltage impressed to the line to secure a speaking current. CONSTITUTION:After receiving a selection signal sent from a shared exchange, a receiving circuit 1 decodes the received signal, compares the decoded result with an individual number to be optionally set up from '0' to '9', and when both the numbers coincide with each other, outputs a coincidence signal. A bell tone generating circuit 2 refers the coincidence signal, switches DC voltage impressed to the line to the signal with the bell frequency and generates a false bell signal. A calling tone generating circuit 3 injects a calling tone to off-hooked telephone set and a loop current restricting circuit 4 restricts the voltage impressed to the line to the minimum current required for speaking in order to guarantee the voltage. Consequently, the terminals of the shared lines can be controlled by two lines the same as the single line requiring no earth line.