Voice band multiplex transmission system
First Claim
1. A voice band multiplex transmission system comprising:
- frequency generating means for generating first and second signals having first and second frequencies respectively;
modulating means connected to said frequency generating means for frequency modulating said first and second signals by the same input information while maintaining the frequency ratio between the said first and second frequencies, the first and second frequencies respectively belonging to predetermined first and second frequency bands and bearing no harmonic relation to each other in the band of a voice circuit;
means for superimposing the modulated first and second signals and an input voice signal on one another and sending them out on a transmission line;
receiver means coupled to said transmission line and comprising pitch extracting means for extracting a pitch frequency of said input voice signal from the signal received from the transmission line;
first comb-characteristic filter means supplied with said received signal to reject the extracted pitch frequency and frequencies of its integral multiples;
first and second filter means respectively supplied with the output from the first comb-characteristic filter means and having the first and second frequency bands as their pass bands;
first and second frequency detecting means, each supplied with the output from one of the first and second filter means to detect one frequency larger than a predetermined threshold;
multiplying means for multiplying one of the detected frequencies of the first and second frequency detecting means by said frequency ratio or a reciprocal of the frequency ratio to coincide with the other detected frequency;
demodulating means for producing a signal of a level corresponding to said other detected frequency and the output frequency of the multiplying means; and
voice output means for obtaining the voice signal from said received signal.
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Accused Products
Abstract
A system for simultaneously transmitting over the same voice circuit a voice signal and input information other than the voice. First and second sine-wave signals which do not bear any harmonic relation to each other in the band of the voice circuit are simultaneously frequency modulated by the input information, and the modulated outputs are superimposed on the voice signal and transmitted. On the receiving side, the pitch frequency of the voice signal is extracted from the received signal, and the pitch frequency and its integral multiples are removed from the received signal to remove a voice component. At this time, at least one of the first and second sine-wave signals is detected. One of these detected outputs is made to have the same frequency as the other frequency. The converted frequency and the detected frequency are demodulated to obtain the original input information.
115 Citations
23 Claims
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1. A voice band multiplex transmission system comprising:
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frequency generating means for generating first and second signals having first and second frequencies respectively; modulating means connected to said frequency generating means for frequency modulating said first and second signals by the same input information while maintaining the frequency ratio between the said first and second frequencies, the first and second frequencies respectively belonging to predetermined first and second frequency bands and bearing no harmonic relation to each other in the band of a voice circuit; means for superimposing the modulated first and second signals and an input voice signal on one another and sending them out on a transmission line; receiver means coupled to said transmission line and comprising pitch extracting means for extracting a pitch frequency of said input voice signal from the signal received from the transmission line; first comb-characteristic filter means supplied with said received signal to reject the extracted pitch frequency and frequencies of its integral multiples; first and second filter means respectively supplied with the output from the first comb-characteristic filter means and having the first and second frequency bands as their pass bands; first and second frequency detecting means, each supplied with the output from one of the first and second filter means to detect one frequency larger than a predetermined threshold; multiplying means for multiplying one of the detected frequencies of the first and second frequency detecting means by said frequency ratio or a reciprocal of the frequency ratio to coincide with the other detected frequency; demodulating means for producing a signal of a level corresponding to said other detected frequency and the output frequency of the multiplying means; and voice output means for obtaining the voice signal from said received signal. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23)
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Specification