To provide the portable telephone system by which excellent speech quality is maintained through simple configuration and control in the case of using the portable telephone system for a weak electric field strength and to provide the transmitter-receiver.

A transmission reception control section 220 in a transmitter- receiver 20 interposed between a public base station and a slave set 30 detects a transmission timing of a slave set 30 based on transmission timing information from the slave set 30, RF switches 202, 208 are switched depending on a detection result to establish selectively a transmission path and a reception path. That is, in the case of a standby state of the slave set 30 as the result of detection, a signal from the public base station 10 received by an antenna 201 is sent from an antenna 209 via an ATT circuit 204, an AMP 205 and a coupler 206 and in the case of transmission of the slave set 30, the signal from the slave set 30 and received by the antenna 209 is sent from an antenna 201 via an AMP 210.