Television receiver with an audio section constructed to automatically receive two channel and stereophonic signals

Claim 3

A method as defined in claim 1 in which said television receiver is selectively switchable between two-channel operation and stereo operation, and in which the step of operating such selective switching is controlled by said audio mode characterizing signal.

Claim 4

A television receiver system for receiving radiated signals including a video signal modulated on a picture carrier, a first audio signal modulated on a first audio carrier of a first predetermined frequency and a second audio signal modulated on a carrier of either a second or a third predetermined frequency, the difference between said second and said third predetermined frequencies being small with respect to the difference between either said second or said third predetermined frequency and said first predetermined frequency, said receiver comprising: first detector means for obtaining, from a receiving signal, said first and said second audio signals modulated respectively on subcarriers having respectively a fourth and either a fifth or a sixth predetermined frequencies, said fourth, fifth and sixth predetermined frequencies being respectively the differences between said first, second and third predetermined frequencies and said picture carrier frequency; first demodulator means for said first audio signal (1) tuned to said fourth predetermined frequency; second demodulator means for said second audio signal (2) tuned to the means between said fifth and sixth predetermined frequencies; second detector means supplied with said subcarriers for obtaining the difference frequency between the frequencies of said subcarriers, namely the difference between either said fifth or said sixth predetermined frequencies and said fourth predetermined frequency, according to whether one of said subcarriers is at said fifth or said sixth predetermined frequency; third demodulator means supplied with said difference frequency by said second detector means and tuned substantially to the approximate mean between the respective differences of said fourth and fifth and said fourth and sixth predetermined frequencies, said third demodulator means providing an output signal having a a characteristic voltage (US; -U 2K) representative of whether said first and second or said first and third or only said first predetermined carrier frequencies are or is received by said receiver; and means for controlling the mode of audio reception in response to said output signal of said third demodulator means.

Claim 5

A television receiver system for receiving radiated signals including a video signal modulated on a picture carrier, a first audio signal modulated on a first audio carrier of a first predetermined frequency and a second audio signal modulated on a carrier of either a second or a third predetermined frequency, the difference between said second and said third predetermined frequencies being small with respect to the difference between either said second or said third predetermined frequency and said first predetermined frequency, said receiver comprising: first detector means for obtaining, from a receiving signal, said first and said second audio signals modulated respectively on subcarriers having respectively a fourth and either a fifth or a sixth predetermined frequencies, said fourth, fifth and sixth predetermined frequencies being respectively the differences between said first, second and third predetermined frequencies and said picture carrier frequency; first demodulator means for said first audio signal (1) tuned to said fourth predetermined frequency; second demodulator means for said second audio signal (2) tuned to the means between said fifth and sixth predetermined frequencies; second detector means supplied with said subcarriers for obtaining the difference frequency between the frequencies of said subcarriers, namely the difference between either said fifth or said sixth predetermined frequencies and said fourth predetermined frequency, according to whether one of said subcarriers is at said fifth or said sixth predetermined frequency; third demodulator means supplied with said difference frequency by said second detector means and tuned substantially to the approximate mean between the respective differences of said fourth and fifth and said fourth and sixth predetermined frequencies, said third demodulator means providing an output signal having a a characteristic voltage (US; -U 2K) representative of whether said first and second or said first and third or only said first predetermined carrier frequencies are or is received by said receiver; and means for controlling the mode of audio reception in response to said output signal of said third demodulator means.

Claim 6

System according to claim 3 further comprising a matrix (5) having the audio signals derived from said first and second discriminators (1, 2) applied thereto, the matrix being connected to and switchable in dependence on the characteristics of the characterizing voltage.

Claim 7

System according to claim 3 wherein the first discriminator (1) is tuned to about 5.5 MHz; the second discriminator is tuned to about 5.75 MHz; and the third discriminator is tuned to about 250 kHz.

Claim 8

System according to claim 3 wherein the characterizing voltages are derived from said mean frequency plus or minus, respectively, the difference between the mean and said second, or third frequency, respectively.

Claim 9

System according to claim 3 wherein the first discriminator (1) is tuned to about 4.5 MHz; the second discriminator is tuned to about 4.752 MHz; and the third discriminator is tuned to about 252 kHz.