JPS6119233A - Channel selection circuit of television receiver - Google Patents

Abstract

PURPOSE:To reduce the number of components of a channel selection circuit by applying AND connection to other circuit of a low channel selection switch of a channel selection circuit to use the circuit in common to channel switching and a muting generation circuit. CONSTITUTION:Two-circuit and 3-contact type switches 9, 10 and 15, 16 for high channel selection and low channel selection operated in interlocking with a channel selection circuit of a TV receiver are arranged. In turning on the switch 9 or 10, terminals (m), (n) or (p), (q) of the switches are opened, the circuit 2 and a switching signal input terminal of a VCO3 are pulled down by a resistor 8 and a low channel is selected. Moreover, when a switch 15 or 16 is changed from OFF to ON, terminals (o), (q) of the switch 16 are turned on momentarily and the shock noise at channel selection is reduced by a muting circuit 6.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a channel selection circuit for a television receiver.

Conventional configuration and its problems In recent years, voltage variable capacitors (hereinafter referred to as ``varicap'')
Voltage-tuned television receivers that use a standard (referred to as ) have come into widespread use.

An audio demodulation circuit for a conventional voltage-tuned television receiver will be described below. FIG. 1 is a circuit block diagram of a conventional voltage-tuned television receiver, in which (1) is an antenna, (2) is a tuning circuit, (3) is a voltage variable local oscillator (hereinafter referred to as rVcOJ), ( 4) is a tuned circuit (2)
(5) is a detection circuit that converts the intermediate frequency into audio, (6) is a mute that reduces shock noise, etc. (7) is an audio output terminal, (8) is a resistor for setting the tuning circuit (2) and VCO (3) to the low channel (channels 1 to 3) of the television;
(9) and (10) are 2-circuit 3-contact shorting type switches for selecting the high channel of the television, (11) and (12) are 4-circuit 3-contact switches for selecting the low channel of the television. These switches (9) to (12) are shorting type switches and operate in conjunction with each other. (13) is a voltage application terminal, (14)
is a tuning voltage generation circuit. Now, if the switch (11) is turned on, the high channel/low channel switching terminals (a), (b), and (c) of the TV set will be as follows.
Since terminals (b) and (C) are open, the high channel/low channel switching signal input terminal of the tuning circuit (2) and VCO (3) becomes low due to the resistor (8).
Low channel is selected. At the same time, since the terminals (f) and (g) of the tuning voltage switching terminals (f) to (h) are turned on, tuning is performed by the tuning voltage applied to the terminal (g). In addition, the shock noise generated during the above switching is reduced by the muting circuit (6) being activated by turning on the terminals (d) and (e) at the moment the switch (11) changes from off to on. .

However, the conventional configuration described above requires a switch circuit exclusively for muting generation, which has the problem of increasing material costs.

OBJECTS OF THE INVENTION The present invention solves the above-mentioned conventional drawbacks, and an object of the present invention is to provide a channel selection circuit for a television receiver that does not require a switch circuit dedicated to muting generation and can be manufactured at low cost.

Structure of the Invention In order to achieve the above object, the channel selection circuit of the television receiver of the present invention includes a plurality of two-circuit, three-contact shorting type switches that operate in conjunction with each other, and one circuit of these switches is The other circuit of the high channel selection switch among the switches is used as a muting generation circuit, and the circuit between the other switch of the low channel selection switch among the switches is used as a muting generation circuit. The configuration is such that it can be connected and used for switching between high and low channels and as a muting generation circuit.

Description of examples Hereinafter, one embodiment of the present invention will be described based on the drawings.

FIG. 2 is a circuit block diagram of a channel selection circuit of a television receiver according to an embodiment of the present invention. Components that are the same as those shown in FIG. . (15) (1, 6) are 2-circuit 3-contact shorting type switches for selecting the low channel of the television, and switches (9) (10) (1
5) (16) works in conjunction. Now, if you turn on the high channel selection switch (9) or (10), the low channel selection switch (15) (
16) terminals (m), (n) and (p) (q) are turned on, the voltage applied to the voltage application terminal (13) is applied to the high channel/low channel of the tuning circuit (2) and V CO (3). Applied to the channel switching signal input terminal, C or (10)
When changes from off to on, terminals (i) (j) or (
k) (Q) is turned on momentarily, so the shock noise at the time of tuning switching is reduced by the muting circuit (6). On the other hand, the low channel selection switch (15) or (16)
) is turned on, the terminals (m) (I)) or (p) (
g) is turned off, the tuned circuit (2) and y CO (3
) is pulled down by a resistor (8) to select the low channel. Also, switch (15) or (16)
) changes from off to on, the terminals (o) and (q) of the switch (16) are turned on momentarily, so the shock noise generated when selecting a channel is reduced by the muting circuit (6).

DETAILED DESCRIPTION OF THE INVENTION According to the present invention, the other circuit of the low channel selection switch is AND-connected and used for both channel switching and muting generation circuits, thereby reducing component costs. can be reduced.

[Brief explanation of the drawing]

FIG. 1 is a circuit block diagram of a tuning circuit of a conventional voltage-tuned television receiver, and FIG. 2 is a circuit block diagram of a tuning circuit of a voltage-tuned television receiver according to an embodiment of the present invention. . (6)...muting circuit, (9) (10)
(15) (16)...2 circuit 3 contact shorting type switch agent Yoshihiro Morimoto Figure 1 Figure 2

Claims (1)

[Claims] It is equipped with a plurality of 1- and 2-circuit, 3-contact shorting type switches that operate in conjunction with each other, one of these switches is used for channel selection, and the other of the switches for high channel selection is used for channel selection. The circuit is used for a muting generation circuit, and the other circuit of the switch for selecting a low channel among the switches is AND-connected to use it for switching between a high channel and a low channel and for a muting generation circuit. This is the configuration of the tuning circuit of the television receiver.