Design and electrical characteristic evaluation for interface circuit in isdn bus wiring system

ISDN basic access interface provides transmission capability of two B channels and one D channel for various telecommunications services. The electrical characteristics of this interface are strictly regulated in CCITT recommendation I.430 to allow up to eight terminals to be connected in a bus wiring system. This paper describes a design method for achieving desired line interface characteristics, including output voltage with specified loads, transmitter output impedance at inactive state, receiver threshold voltage and cut-off frequency of a low-pass filter. The electrical characteristics of the line interface circuit based on the proposed design are measured by using practical bus wiring systems and are confirmed to satisfy recommendation I.430.