Patent GB-1431795-A (GB)
Title: Channel tuning apparatus including an unused-channel skip circuit
IPC: H04N5/44
Filed: 1973-04-26
Abstract: 1431795 Channel tuning arrangements SONY CORP 26 April 1973 [27 April 1972] 19846/73 Heading H3Q In a channel tuning apparatus including an unused channel skip circuit, the circuit comprising a pulse generator 9 which oscillates when a control signal exists, a pulse counting means 17 connected to the pulse generator, potentiometers 23 1 -23 12  connected to the outputs of the pulse counting means and an electronic tuning circuit (not shown) including a variable reactance element connected to tuning voltage output terminal t vc  which is commonly connected to the outputs of the potentiometers, a tuning voltage detecting circuit 24 is connected to the tuning voltage output terminal and a pulse generator control means 6, 7 is connected between the pulse generator 9 and the tuning voltage detecting circuit 24 to maintain an oscillating operation of the pulse generator 9 when the tuning voltage at the tuning voltage output terminal t vc  is outside a predetermined voltage range.  As shown remote control of a television tuner is obtained by two different frequency fu and fd ultrasonic signals to provide upward or downward channel selection. When the fu signal is received by a detector 3u the output from a differentiating circuit 20u makes transistors 18d and 18u of a bi-stable circuit 19 on and off and the output from a transistor 7 turns off and starts the pulse generator 9. The anode of a diode 11d and the base of a transistor 12d are grounded through a diode 22d and the transistor 18d so that the output pulse from the generator 9 are applied through a diode 11u to a transistor 12u only, which is switched on and off as determined by the pulses from the generator 9. When the transistor 12u is turned on it produces a negative pulse which is applied via a diode 15u to the first guide electrodes G1 of a counting tube 17 and via an integrating circuit 14u which produces a delay to the second guide electrodes G2 so as to sequentially glow discharge the cathodes k1 to k12 to perform upward channel selection by the tuning voltage at t vc  which is applied to a variable capacitance diode of an electronic tuner. When a downward remote control signal fd is received at 1 the circuit components 3d, 20d, 12d and 14d operate in a similar manner to the corresponding components for upward selection so that the counting tube 17 counts downwards. An unused channel position such as corresponding to channel 2 may be skipped by moving the slider of the associated potentiometer 23 2  to zero potential. Then on the output state of the counting tube changing to cathode k 2  zero output at t vc  causes a transistor 24 to turn off and produce a positive output pulse which even if the input to 1 has ended causes transistor 6 to conduct. This turns off the transistor 7 so as to maintain the pulse generator 9 operative to stop the counting tube 17 to the next cathode k 1  or k 3 . The tuning voltage now at t vc  biases the transistor 24 on and provided the control signals applied at 1 has also ended the pulse generator stops and the channel 1 or 3 is selected. Also when the unused channel is detected the oscillating period of the pulse generator 9 may be shortened to speed up the channel selection operation. In a modification (Fig. 3, not shown) the counting tube 17 is replaced by a reversible counter (27) including bi-stable circuits and a decoder (31). Specification 1,208,849 is referred to.