Four channel record reproducing apparatus with muting of speakers not used for stereo or monaural records

Claim 2

A phonograph record reproducing apparatus for interchangeably playing back monaural, stereo and four channel records, said monaural record having an unmodulated signal recorded in a single groove thereof, said stereo records having two unmodulated signals respectively recorded on two side walls of a single groove thereof, said four channel records having two multiplex signals respectively recorded on two side walls of a single groove thereof, one of the two multiplex signals including one unmodulated sum signal combining first and second of the four channel signals and one modulated signal paired therewith wherein a carrier signal is modulated responsive to a difference signal combining the first and second channel signals, the other of the two multiplex signals including another unmodulated sum signal combining third and fourth of the four channel signals and another modulated signal paired therewith wherein the carrier signal is modulated responsive to a difference signal combinig the third and fourth channel signals; said reproducing apparatus including two signal processing means each of which processes an associated one of the two multiplex signals, each of said signal processing means comprising separator means for separating the unmodulated sum signal and the paired modulated signal from the associated multiplex signal; demodulator means for demodulating the paired modulated signal separated by said separator means; detector means for detecting the carrier component of the paired modulated signal separated by said separator means; control signal generator means for rectifying the carrier component detected by said detector means to produce a control signal; muting circuit means connected to the output circuit of said demodulator means, means responsive to the control signal having a level exceeding a predetermined level for selectively causing the muting circuit means to pass the output signal of said demodulator means, and mean responsive to the control signal having a level below the predetermined level for selectively causing the muting circuit means to interrupt the output signal of said demodulator means; matrix circuit means responsive to the output signal of said muting circuit means and the unmodulated sum signal separated by said separator means for individually providing the two channel signals paired with the demodulated signal in the associated multiplex signal.

Claim 3

The reproducing apparatus as defined in claim 1 further comprising four speakers arranged with respect to a listener so that a first speaker is placed at the front and on one side for generating sound in response to the first channel signal, a second speaker is placed at the rear and on the one side for generating sound in response to the second channel signal, a third speaker is placed at the front and on the other side for generating sound in response to the third channel signal, and a fourth speaker is placed at the rear and on the other side for generating sound in response to the fourth channel signal; and wherein each of said two signal processing means further comprises second muting circuit means cOntrolled in response to the control signal for selectively passing the second (or the fourth) channel signal from said matrix circuit means to the second (or the fourth) speaker when the level of the control signal exceeds the predetermined level and for selectively interrupting the second (or the fourth) channel signal when the level of the control signal is below the predetermined level.

Claim 4

The reproducing apparatus as defined in claim 1 wherein each of said two signal processing means further comprises first circuit means and second circuit means having a predetermined frequency response for respectively receiving the first (or the third) channel signal and the second (or the fourth) channel signal from said matrix circuit means, the first and second circuit means respectively including circuit means responsive to the control signal for increasing the response in a high frequency range when the control signal level exceeds the predetermined level.

Claim 5

The reproducing apparatus as defined in claim 1 wherein each of said two signal processing means further comprises indication lamp circuit means for lighting a lamp in response to the control signal when its level exceeds the predetermined level and for putting out the lamp in response to the control signal when its level is below the predetermined level.

Claim 6

The reproducing apparatus as defined in claim 1 wherein each of said two signal processing means further comprises switching circuit means and indication lamp circuit means, said switching circuit means including a first switching transistor which is switched to a conductive state in response to the control signal applied to the base electrode thereof when the level of the control signal exceeds the predetermined level and which is switched to a non-conductive state when the level of the control signal is below the predetermined level, and a second switching transistor connected to be controlled by the output of the first switching transistor, said second switching transistor being switched to a non-conductive state in response to said first switching transistor when in the conductive state and switched to a conductive state in response to said first switching transistor when in the non-conductive state; said indication lamp circuit means including first and second indication lamps respectively connected to the collector electrodes of the first and second switching transistors, whereby during the reproduction of the four channel record, the first indication lamp is lighted in response to the conductive state of the first switching transistor, and during the reproduction of the one channel or two channel record, the second indication lamp is lighted in response to the conductive state of the second switching transistor.

Claim 7

A phonograph record reproduction system for interchangeably playing back monaural, stereo, and four channel records, said monaural and stereo records having unmodulated signals recorded thereon, said four channel records having modulated and unmodulated signals recorded thereon in the form of a synchronized pair of signals, one of said pair being a modulated signal and the other of said pair being an unmodulated signal, said reproduction system comprising: pick-up means, first separator means connected to said pick-up means for separating the modulated signal and the paired unmodulated signal from the signal reproduced by said pick-up means from a four channel record, first demodulator means for demodulating the modulated signal separated by said first separator means, first detector means having a tuned circuit of high selectivity with a tuned frequency which coincides with the carrier frequency of said modulated signal in order to detect the carrier frequency indicating the presence of the first modulated signal, first control signal generator means for rectifying the detected carrier frequency and producing a first control signal responsive thereto, first muting circuit means connected to the output circuit of the first demodulator means, first switching circuit means operated responsive to said first control signal for passing the output signal of said first demodulator means to the first muting circuit means during the presence of the first control signal and interrupting the output signal at the first muting circuit means when the first control signal is nonexistent, first matrix circuit means responsive to the output signal of the first muting circuit means and the synchronized unmodulated signal for individually providing first and second channel signals during the presence of the output signal of the first muting circuit means and for providing two signals responsive to the paired unmodulated signal during a nonexistence of the output signal of said first muting circuit means, second separator means for separating the second modulated signal and the paired unmodulated signal from the signal reproduced by said pick-up means, second demodulator means for demodulating the second modulated signal separated by said second separator means, second selective amplifier means having said tuned circuit associated therewith to detect the carrier frequency in response to the second modulated signal, second control signal generator means for rectifying the carrier frequency detected by said second selective amplifier means and producing a second control signal responsive thereto, second muting circuit means connected to the output circuit of the second demodulator means, second switching circuit means responsive to the second control signal for passing the output signal of the second demodulator means through the second muting circuit means during an existence of the second control signal and interrupting the output signal of the second demodulator means at the second muting circuit means during a nonexistence of the second control signal, and second matrix circuit means responsive to the output signal of the second muting circuit means and the unmodulated signal corresponding to the second modulated signal for individually providing the third channel signal and the fourth channel signal during an existence of the output signal of the second muting circuit means and providing two signals the same as the unmodulated signal corresponding to the second modulated signal during a nonexistence of the output signal of said second muting circuit means.

Claim 8

A phonograph record reproduction system for interchangeably playing back monaural, stereo, and four channel records, said monaural and stereo records having unmodulated signals recorded thereon, said four channel records having modulated and unmodulated signals recorded thereon in the form of a synchronized pair of signals, one of said pair being a modulated signal and the other of said pair being an unmodulated signal, said reproduction system comprising: pick-up means, first separator means connected to said pick-up means for separating the modulated signal and the paired unmodulated signal from the signal reproduced by said pick-up means from a four channel record, first demodulator means for demodulating the modulated signal separated by said first separator means, first detector means having a tuned circuit of high selectivity with a tuned frequency which coincides with the carrier frequency of said modulated signal in order to detect the carrier frequency indicating the presence of the first modulated signal, first control signal generator means for rectifying the detected carrier frequency and producing a first control signal responsive thereto, first muting circuit means connected to the output circuit of the first demodulator means, first switching circuit means operated responsive to said first control signal for passing the output signal of said first demodulator means to the first muting circuit means during the presence of the first control signal and interrupting the output signal at the first muting circuit means when the first control signal is nonexistent, first matrix circuit means responsive to the output signal of the first muting circuit means and the synchronized unmodulated signal for individually providing first and second channel signals during the presence of the output signal of the first muting circuit means and for providing two signals responsive to the paired unmodulated signal during a nonexistence of the output signal of said first muting circuit means, second separator means for separating the second modulated signal and the paired unmodulated signal from the signal reproduced by said pick-up means, second demodulator means for demodulating the second modulated signal separated by said second separator means, second selective amplifier means having said tuned circuit associated therewith to detect the carrier frequency in response to the second modulated signal, second control signal generator means for rectifying the carrier frequency detected by said second selective amplifier means and producing a second control signal responsive thereto, second muting circuit means connected to the output circuit of the second demodulator means, second switching circuit means responsive to the second control signal for passing the output signal of the second demodulator means through the second muting circuit means during an existence of the second control signal and interrupting the output signal of the second demodulator means at the second muting circuit means during a nonexistence of the second control signal, and second matrix circuit means responsive to the output signal of the second muting circuit means and the unmodulated signal corresponding to the second modulated signal for individually providing the third channel signal and the fourth channel signal during an existence of the output signal of the second muting circuit means and providing two signals the same as the unmodulated signal corresponding to the second modulated signal during a nonexistence of the output signal of said second muting circuit means.

Claim 9

The record reproducing apparatus as defined in claim 6 further comprising first circuit means and second circuit means having a predetermined frequency response and respectively receiving the first channel signal or the unmodulated signal corresponding to the first modulated signal and the second channel signal or the unmodulated signal corresponding to the first modulated signal from the first matrix circuit means, the first and second circuit means respectively including circuit means responsive to said first control signal for increasing the response in high frequency range during the existence of the first control signal, and third circuit means and fourth circuit means having the same frequency response as that of the first and second circuit means and respectively receiving the third channel signal or the unmodulated signal corresponding to the second modulated signal and the fourth channel signal or the unmodulated signal corresponding to the second modulated signal from the second matrix circuit means, the third and fourth circuit means respectively including circuit means similar to the circuit means included in said first and second circuit means responsive to said second control signal for increasing the response in high frequency range during the existence of the second control signal.

Claim 10

The record reproducing apparatus as defined in claim 6 further comprising third muting circuit means receiving the second channel signal or the unmodulated signal corresponding to the first modulated signal from the first matrix circuit means, and fourth muting circuit means recieving the fourth channel signal or the unmodulated signal corresponding to the second Modulated signal from the second matrix circuit means, wherein said first switching circuit means also passes the second channel signal through the third muting circuit means during the existence of the first control signal and interrupting the second channel signal or the unmodulated signal corresponding to the first modulated signal at the third muting circuit means during the nonexistence of the first control signal, and wherein said second switching circuit means also passes the fourth channel signal through the fourth muting circuit means during the existence of the second control signal and interrupting the fourth channel signal or the unmodulated signal corresponding to the second modulated signal at the fourth muting circuit means during the nonexistence of the second control signal.

Claim 11

The record reproducing apparatus as defined in claim 6 further comprising lamp circuit means including a lamp, wherein said first switching circuit means also pass a current through said lamp circuit means during the existence of the first control signal thereby to indicate that the four channel record is being reproduced.