A base transceiver station in a wireless local loop system using a personal handy-phone system constituted by a plurality of cell stations, each accommodating a plurality of subscriber units, a hybrid section integrally handling signals transmitted and received by the plurality of cell stations via a single antenna, and a multiplexing/demultiplexing unit integrally handling the signals transferred between the plurality of cell stations and an existing network, thereby enabling construction of a wireless local loop system which is small in size, can expand the service area without an increase of interference with other base transceiver stations, has a good affinity with existing networks, is provided with ISDN functions, and, at the same time, provides backup against faults and improves the transmission quality and reliability.