| 摘要 |
PURPOSE:To discriminate the abnormality of a master telephone set and that between the master and slave telephone sets prior to dial operation by detecting the existence of a tone signal generated from the slave set, received by the master set and fed back and converting the output of a detecting circuit for the tone signal into a voice signal. CONSTITUTION:The master telephone set 4 provided with a master telephone set transmitting/receiving device 22 is arranged adjacently to a telephone set 2 and also connected to a telephone line 8. Plural slave telephone set 6 provided with transmitting/receiving devices 36 respectively are arranged. A tone signal generating circuit 52 in the slave set 6 is actuated, a generated tone signal is modulated 56 and amplified 58 at its high frequency and the amplified signal is transmitted from an antenna 18A. The transmitted tone signal is received by a master set 4, amplified at its high frequency and converted at its frequency by a high frequency amplifier/frequency converter 24 and demodulated 26 and the demodulated tone signal 26 is checked 28 to detect the tone signal. The tone signal is modulated 32, amplified 34 and transmitted 20A. The transmitted signal is received from an antenna 18A of the slave set 6, converted 38 at its frequency, demodulated 40 and applied to a speaker 14 and a tone signal detecting circuit 42. A drive controller 44 is actuated by an output from the circuit 42 and a voice is composed 46 and displayed 48 to detect and display the legality/illegality of the transmission/reception. Thus, the slave set 6 discriminates the defect of the system prior or dial operation and useless operation is saved. |
