| 摘要 |
PURPOSE:To reduce the number of components by using each high frequency circuit conventionally provided to each transmission/reception unit in common as one common circuit. CONSTITUTION:A received signal from each radio telephone set inputted from a reception antenna 22 is converted into a lower frequency than a radio frequency by an input frequency conversion circuit 27 and inputted to a MODEM unit 25. The received signal converted into a low frequency and inputted to the MODEM unit 25 is demodulated into a voice band signal by a demodulation circuit 30 and the result is sent to a telephone exchange 24. The voice band signal outputted from the telephone exchange 24 is supplied to the MODEM unit 25, where it is modulated to a transmission signal by a modulation circuit 31. Then the transmission signal sent from the unit 25 is converted into a radio frequency by an output frequency conversion circuit 33, automatically controlled to a specified power by a power control circuit and sent from a transmission antenna 21. Thus, no high frequency circuit is required to be assembled in each MODEM unit 25. |
