INTERFACE-KRETSANORDNING FOR ATT UPPRETTA KOMMUNIKATIONSVEGAR MELLAN EN TELEFONKOMMUNIKATIONSLEDNING OCH EN BUSSKRETSANORDNING

摘要

MONOBUS INTERFACE CIRCUIT USING OPTO-COUPLED HYBRIDS In order to reduce the signal loss in a telephone line switching and conferencing system there is interposed between each line and the switching matrix a monobus port circuit arranged to convert a transmitted telephone signal into an equivalent current source. An opto-coupled hybrid replaces the port circuit transformer and served to provide the desired voltage to current conversion. The currents from several monobus circuits are added in a bus resistor before distribution back to the individual monobus circuits as a voltage where the original signal is subtracted from the bus signal. The resultant signal is transmitted to the telephone receiver via the opto-coupled hybrid. When the switching matrix crosspoint resistance is negligible, the component of the bus voltage measured at the current source output which results from current generated from each port circuit is equal and opposite in magnitude to the voltage generated in the port circuit. In any given line these voltages cancel each other, thereby eliminating the feedback signal.