JPS6023835Y2 - Muting device for tape recorder with radio - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a muting device for reducing switching noise in a tape recorder with radio.

FIG. 1 is a circuit diagram of a tape recorder with a radio equipped with a conventional muting device, and its operation will be explained item by item below.

a At the time of radio reception, the movable contact C of the teleco/radio selector switch 2 is set to R.
side, that is, on the radio side, 10B is supplied to the power terminal 2 of the radio 11.

At this time, the radio waves received by the antenna 10 enter the input terminal 1 of the radio 11, so an audio signal is output from the output terminal 3 of the radio 11, is IO controlled by the volume control polyolium 7, and is amplified by the main amplifier 8. The sound is output from the speaker 9.

b At the time of telephonic playback, the recording/playback selector switch 3t3-at3-by 3
-ct Each movable contact C of 3-d is on the P side, and the teleco/
Since the movable contact C of the radio selector switch 2 is on the T side, that is, on the teleco side, 10B is connected to the power terminal 2 of the recording/playback amplifier 5.
is supplied.

Also, since the tape playback signal from the recording/playback head 6 is input to the input terminal 1 of the amplifier 5, the output terminal 3 of the amplifier 5 receives the tape playback signal from the recording/playback head 6.
A playback signal is output from the main amplifier 8 through a resistor 25, a volume control polyurethane 7, and amplified by a main amplifier 8, and a playback sound is output from a speaker 9.

When recording C radio, the recording and playback switch 3.3-a, 3-by 3
-at 3-d each movable contact C is on the R side, and the teleco/
Since the movable contact C of the radio selector switch 2 is on the T side, that is, on the teleco side, the RADIO
10B is supplied to the power supply terminal 2 of ll.

Furthermore, 10B is also supplied to the power supply terminal 2 of the bias oscillator 15.

With this configuration, the audio output from the radio 11 is output from the speaker 9 via the volume control polyurethane 7 and the main amplifier 8.

Also, at this time, the audio output of the radio 11 enters the input terminal 1 of the recording/playback amplifier 5 via the recording/playback switch 3-c via another route, is amplified and outputted from the output terminal 3, and is output from the resistor 1.
2. After passing through the low frequency attenuation circuit formed by the capacitor 13, the signal is superimposed with the AC bias from the output terminal 1 of the bias oscillator 15 and is applied to the recording/reproducing head 6.

At this time, 10B voltage is also supplied to one terminal T of the resistor 19 of the muting circuit 18, so the transistor 24 is turned on, and the p contact of the recording/playback switch 3-b is shorted to ground. become.

In other words, the teleco playback output is muted.

d Muting circuit In this case, as explained in section C above, during radio recording, the p contact of the recording/playback switch 3-b is shorted to ground, and the output of the recording/playback amplifier 5 is muted. .

After this state, when the teleco operation button is activated to cancel recording and enter the playback state, the recording/playback selector switch 3, 3-a
, 3-b, 3-C, 3-d each movable contact C is P
Move to the side.

At this time, 10B is no longer supplied to one terminal of the resistor 19, but the charge in the capacitor 20 is discharged through the resistors 21 and 22.

Therefore, the output from the recording/reproducing amplifier 5 is muted and does not come out from the speaker 9 for a short time determined by these time constants.

That is, it mutes the switching noise that occurs when recording is cancelled.

A drawback of this prior art is that it does not work to mute switching noise when switching from radio to teleco.

An object of the present invention is to provide a muting device that mutes and reduces switching noise when switching from radio to teleco.

For this reason, the present invention applies a voltage of 10B to the recording/playback amplifier of the telephone even during radio reception, that is, a voltage of 10B is constantly applied to the recording/playback amplifier to reduce switching noise between the radio and the telephone. The purpose is to mute the output of the recording/playback amplifier when receiving radio signals.

A specific embodiment of the present invention is shown in FIG.

Next, this operation will be explained, and the same parts as in FIG. 1 are denoted by the same reference numerals.

To explain the differences from FIG. 1, first, [1] 10B voltage is always applied to the power supply terminal 2 of the recording/playback amplifier 5.

Therefore, the resistor 4 is connected to the common terminal C of the teleco/radio changeover switch.

Next [2] Apply a voltage of 10B to the muting operation terminal T of the muting circuit 18 (the terminal T connected to the diode 17 of the resistor 19) during the radio mode, and mute the teleco playback output during the radio mode. .

For this purpose, the terminal T is connected to the anode side of the diode 17.

By carrying out (1) and (2) above, it became possible to constantly apply the sub-B voltage to the recording/reproducing amplifier 5, and it was possible to reduce switching noise between radio and telephony.

By doing this, the transistor 2 of the muting circuit 18 can be used during radio reception as well as when recording radio.
4 can be turned on to mute the output of the recording/playback amplifier 5, and when switching from radio to teleco, the capacitor 20
Since the transistor 24 is turned on during charging and then muted, the present invention can reduce switching noise even when switching from radio to teleco, making it convenient for practical use.

[Brief explanation of drawings]

FIG. 1 is a block diagram of a tape recorder with a radio equipped with a conventional muting device, and FIG. 2 is a block diagram of an example of a tape recorder with a radio equipped with the muting device of the present invention. 2...Teleco/radio selector switch, 3...
... Recording/playback selector switch, 5... Recording/
Reproduction amplifier, 16...muting circuit.

Claims (1)

[Scope of utility model registration request] Connect the power supply terminal of the recording/playback amplifier to the common contact of the teleco/radio selector switch and apply power voltage to the recording/playback amplifier during radio operation as well as during tape recorder operation.
Connect the muting operation terminal of the muting circuit connected to the fixed contact on the playback side of the first recording/playback switch whose common terminal is connected to the output of the recording/playback amplifier to the fixed contact on the radio side of the tele/radio switch. What is claimed is: 1. A muting device for a tape recorder with a radio, characterized in that the muting device is connected to the common contact of the teleco/radio changeover switch via the radio-side fixed contact and the common contact of the second recording/playback changeover switch.