Channel selecting apparatus for television receiver having means to cut off amplifying transistor for predetermined time

Claim 2

A channel selecting apparatus for a television receiver, comprising an electronic tuner for selecting a channel depending on the amount of the tuning voltage supplied to the input terminal thereof, a plurality of channel selecting buttons on which a signal is induced by being touched by a hand, a plurality of amplifying circuits each connected to each of the channel selecting buttons, a plurality of switching circuits each connected to each of the amplifying circuits, a plurality of voltage regulators each connected to the output terminal of each of the switching circuits, a plurality of reverse voltage blocking diodes each connected to the output terminal of each of the voltage regulators, means for connecting the output terminal of each of the reverse voltage blocking diodes to the input terminal of the electronic tuner, a plurality of control circuits each connected to each of the channel selecting buttons for deriving a part of the induced signal to effect control, a malfunction preventing circuit connected to all of the output terminals of the control circuits, means for connecting the output terminal of The malfunction preventing circuit to all of the amplifying circuits, a constant voltage source, and means for connecting the constant voltage sources to the switching circuits and the malfunction preventing circuit, whereby the amplifying circuit and the switching circuit connected to a desired channel selecting button are activated by a signal induced on the desired channel selecting button to supply an output of the constant voltage source to the voltage regulator connected to the latter switching circuit to adjust the voltage which is supplied through the corresponding reverse voltage blocking diode to the input terminal of the electronic tuner, while the malfunction preventing circuit is activated by the induced signal supplied thereto through the corresponding control circuit to produce, after the lapse of a constant time, a voltage sufficient for cutting off the amplifying circuits which is supplied to the amplifying circuits in a reverse-biassing manner.

Claim 3

A channel selecting apparatus for a television receiver, comprising an electronic tuner for selecting a channel depending on the amount of the tuning voltage supplied to the input terminal thereof, a plurality of channel selecting buttons, a plurality of signal amplifying transistors connected to the plurality of channel selecting buttons whose emitters are connected in common, a plurality of switching elements whose control terminals are connected to the output terminals of the signal amplifying transistors, respectively, whose input terminals are connected to a common resistor, and whose output terminals are connected with capacitors, respectively, a constant voltage source connected to the input terminals of the switching elements through the common resistor, a plurality of voltage regulators connected to the output terminals of the switching elements, respectively, a plurality of first reverse voltage blocking diodes connected to the voltage regulators, respectively, and to the electronic tuner, the signal amplifying transistor and the switching element connected to a desired channel selecting button being turned on by a signal supplied to the desired channel selecting button, the output of the constant voltage source being supplied to the input terminal of the electronic tuner through the latter switching element, the voltage regulator connected thereto, and the first reverse voltage blocking diode connected thereto, a plurality of second reverse voltage blocking diodes whose anodes are connected to the bases of the signal amplifying transistors, respectively, and whose cathodes are connected in common, a first transistor operating by being supplied with a signal at its base from said commonly connected cathodes, a second transistor connected to the output terminal of the first transistor and to whose collector a discharging resistor and an operating time setting capacitor are connected, and a third reverse voltage blocking diode connected between the common emitter of the signal amplifying transistors and the collector of the second transistor, whereby a voltage sufficient for cutting off the signal amplifying transistors is produced after the lapse of a constant time determined by the collector current of the second transistor and the operating time setting capacitor and is supplied to the signal amplifying transistors in a reverse-biassing manner.

Claim 4

A channel selecting apparatus for a television receiver, comprising an electronic tuner for selecting a channel depending on the amount of the tuning voltage supplied to the input terminal thereof, a plurality of channel selecting buttons, a plurality of signal amplifying transistors connected to the plurality of channel selecting buttons whose emitters are connected in common, a plurality of switching elements whose control terminals are connected to the output terminals of the signal amplifying transistors, respectively, whose input terminals are connected to a common resistor, and whose output terminals are connected with capacitors, respectively, a constant voltage source connected to the input terminals of the switching elements through the common resistor, a plurality of voltage regulators connected to the output terminals of the switching elements, respectively, a plurality of first reverse voltage blocking diodes connected to the voltage regulators, respectively, and to the electronic tuner, the signal amplifying transistor and the switching element connected to a desired channel selecting button being turned on by a signal supplied to the desired channel selecting button, the output of the constant voltage source being supplied to the input terminal of the electronic tuner through the latter switching element, the voltage regulator connected thereto, and the first reverse voltage blocking diode connected thereto, a plurality of second reverse voltage blocking diodes whose anodes are connected to the bases of the signal amplifying transistors, respectively, and whose cathodes are connected in common, a first transistor operating by being supplied with a signal at its base from said commonly connected cathodes, a second transistor connected to the output terminal of the first transistor and to whose collector a discharging resistor and an operating time setting capacitor are connected, and a third reverse voltage blocking diode connected between the common emitter of the signal amplifying transistors and the collector of the second transistor, whereby a voltage sufficient for cutting off the signal amplifying transistors is produced after the lapse of a constant time determined by the collector current of the second transistor and the operating time setting capacitor and is supplied to the signal amplifying transistors in a reverse-biassing manner.