| 摘要 |
PURPOSE:To improve the talking quality when it is not required to mind wire- trapping by using an electric field detection circuit so as to detect an electric field strength and reducing transmission power when the electric field strength is high and selecting the circuit so as not to use scrambling. CONSTITUTION:A slave set and a master set use detection circuits 17,27 to detect an electric field strength of a reception signal and when the electric field strength is smaller than a prescribed value set by comparators 18, 28, changeover devices 16a, 16b, 26a, 26b of both sets are thrown to a terminal (a) and the transmission reception signal is processed by using scramblers 13a, 13b, 23a, 23b. On the other hand, when the electric field strength detected by the detection circuits 17, 27 is larger than a prescribed value, a switching control signal from the control circuits 19, 29 is sent via transmission circuits 12, 22, and received by reception circuits 11, 21 of the opposite party. When the control circuits 19, 29 discriminate it that the switching control signal is received from the opposite party and the electric field strength of its own set reaches a prescribed value or larger, the transmission output and the scramblers 13, 23 are selected. |
