JPS54139304A - Dial signal transmission system - Google Patents

Abstract

PURPOSE:To prevent the malfunction dependent upon sound or noise to prevent the dial distortion of a DC loop by receiving control signals, which accord to dial signals and short-circuit signals of a telephone set, in a base station and detecting respective control signals and transmitting dial signals to an exchange. CONSTITUTION:In radio mobile station 1, oscillator 12 generates control signals according to dial signals of a telephone set, and oscillator 13 generate control signals B according to short-circuit signals of the telephone set, and signals A and B are transmitted with carrier waves different from each other by radio transmitter 14. Meanwhile, in base station 2, respective carrier waves are received by receiver 22, and signals A and B are detected by signal detector circuits 27 and 28 on a basis of the output of receiver 22. Then, AC stopping choke coil 34 is short-circuited in 32 by the output of circuit 28, and the DC loop circuit is switched in 31 by the output of circuit 27, thereby transmitting dial signals to exchange 3. As a result, the malfunction dependent upon sound or noise can be prevented, and the generation of dial distortion can be prevented at a DC loop short-circuit time or opening time.