JPH0227640Y2 - - Google Patents

Description

[Detailed Description of the Invention] [Field of Application of the Invention] The present invention relates to a circuit for muting noise generated when switching to a car stereo based on a radio broadcast reception state in a car stereo combination with a radio.

[Background of the idea]

There are two ways to switch to the car stereo when receiving radio broadcasts:

1 If you insert a cassette tape while the radio is on, it will switch to the car stereo.

2 When playing the radio, press the play button with a cassette tape inserted.

Conventionally, muting was not applied at the above two times to eliminate the switching noise.

[Purpose of invention]

The purpose of this invention is as follows.

1 When the cassette tape is inserted, the deck turns on, but muting is applied at this time.

2 Muting is applied when you press the switch to turn on the deck when receiving radio broadcasts with a cassette tape inserted.

3 Even if I press the digital ON switch when not receiving radio signals, muting does not work.

[Summary of the idea]

In order to solve the purpose of item (3) above, the present invention includes a switch in the power supply circuit that turns on when a tape is inserted.
As a result, muting is applied only when the tape is inserted and when the deck ON switch is operated. Also, muting occurs when inserting the tape. Further, the purpose is to prevent abnormal muting other than when necessary by switching the radio status instruction signal so that the muting is activated only in the radio status, and so that the muting is not applied in any other status than the radio status.

[Example of idea]

An embodiment of the present invention will be described using the circuit diagram shown in the figure. The audio signal output 1 is amplified by a power amplifier 2 and reproduced as audio from a speaker 3. When the switching transistor 24 is turned on, the audio signal output is short-circuited to ground with low impedance, so that muting is applied. Below, I will explain how to apply this muting.

A voltage protection circuit is formed by connecting the +B voltage 4, a switch 8 that turns on when the tape is inserted, a resistor 9 in series, and a Zener diode 9 in parallel. The emitter of the switching transistor 14 and the resistor 11 are connected to this. Furthermore, a resistor 12 is connected to the base of the switching transistor 14,
It is connected via a diode 13 to a switch 17 that turns on the deck.

The following explains how the above-mentioned configuration accomplishes the purpose of item (3).

1 When the cassette tape is inserted, the deck control section 6
Since the signal goes to , the deck turns on, but at this time switch 8, which turns on when the cassette tape is inserted, closes, so the differentiating circuit of capacitor 25 and resistor 26 works, and diode 27 and resistor 23
Since the switching transistor 24 is turned ON for a certain period of time via , muting is applied.

2. When a cassette tape is inserted, the switch 8 is in a closed circuit, so a DC voltage is applied to the switching transistor 14. In this state, when the switch 17 that turns on the deck is closed, a signal is sent to the deck control section 6 and the deck is turned on.
However, at the same time, the switching transistor 14 also turns on, so a positive DC voltage is generated at the collector, and the differentiating circuit of the capacitor 18 and resistor 19 works, so the diode 22 and resistor 23
The switching transistor 24 is turned on for a certain period of time via. Furthermore, since the radio is in the reception state, the radio status instruction signal 7 is LOW, and the switching transistor 20 is OFF, so muting is applied.

3 When not receiving radio broadcasts, the radio status instruction signal terminal 7 is at a high potential (low potential when receiving radio broadcasts), so the switching transistor 20 is in the ON state, so the deck ON switch 17 is closed. Do not perform muting movements even if the In this way, unnecessary muting operations were not performed, and the purpose of item (3) could be achieved.

[Effect of idea]

The effect of the present invention is that the purpose of item (3) is satisfied, that is, the following effects are achieved.

1 Muting occurs when inserting a cassette tape.

2 When receiving radio with a cassette tape inserted, muting is applied when the deck ON switch is turned on.

3 Turn on the switch when not receiving the radio.
Muting does not apply even if it is turned on.

[Brief explanation of the drawing]

The figure is a circuit diagram showing one embodiment of the present invention. 1... Audio signal output, 2... Power amplifier, 3
...Speaker, 6...Deck control unit, 7...Radio status instruction signal, 8...Switch turned ON when tape is inserted, 14...Switching transistor,
17... Switch to turn on the deck, 20...
Switching transistor, 24...Switching transistor.

Claims (1)

[Scope of utility model registration request] A switch that turns on when the tape is inserted is inserted into the power supply circuit, and the rising voltage when the switch is turned on activates the differentiating circuit so that the muting circuit works, and when the switch is turned on, the power supply voltage of the switching transistor is When a switch is operated to turn on the deck, the switching transistor is turned on, and the rising voltage at this time activates the differentiating circuit to operate the second mutating circuit. , ON-OFF of switching transistor in radio reception state
A radio control switching transistor is provided to control the radio control switching transistor, and when this radio control switching transistor is ON, the second muting circuit is not activated, and when receiving radio, the radio control switching transistor is OFF and the second muting circuit is When muting is activated and the radio is not received, the radio control switching transistor is activated.
A mutating circuit characterized in that the second mutating circuit is turned ON and the second mutating circuit is prevented from working.