| 摘要 |
PURPOSE:To transmit signal information without lowering a voice signal by intermitting a tone signal of a frequency band not overlapped with a voice signal frequency by means of the signal information to be transmitted and applying PCM coding the intermittent signal, synthesizing it with a PCM code of the voice signal and transmitting/receiving it. CONSTITUTION:A signal generated by an oscillator 7 is subjected to frequency division 8, converted into a tone signal in 3.825kHz of an idle frequency band of the voice signal and intermitted by a switching circuit 9 depending on the binary value of signal information SS to be transmitted. The intermitted tone signal is converted into a PCM code of linear characteristic by a coder 10, the PCM of the signal information is added to the PCM code of the voice signal by an adder 11 and transmitted to a repeater after being converted into an ADPCM code by a coder 4. On the other hand, when the ADPCM signal is received, it is converted into the PCM code by a decoder 5 and transmitted to a digital filter 12. Then the signal is decomposed into the signal component of 3.4-4.0kHz and the voice signal of 0.3-3.4kHz, the signal component is subjected to level identification 13 and the voice signal component is converted into the PCM code with companding by a compressor 6 and then demodulated into the voice signal. |
