JPS6034093Y2 - Tape recorder recording switching circuit - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to an improvement of a recording switching circuit of a tape recorder.

When the tape recorder is switched to recording mode, a certain amount of startup time is required for the recording amplifier to operate normally due to charging of the capacitor within the recording amplifier.

If a recording signal is added during this rise time, a distorted signal will be recorded on the magnetic tape.

Also, when switching from the recording state to another state, such as a pause state, the recording amplifier gradually stops its operation by discharging the capacitor, etc., so if a recording signal is applied during this fall time, the magnetic tape will not be recorded. A distorted signal is recorded.

Therefore, when switching to the recording state, it is necessary to cut off the recording signal until the recording amplifier returns to normal operation, and when recording is stopped, it is required to cut off the recording signal immediately.

For this purpose, for example, a recording switching circuit shown in FIG. 1 has been conventionally used.

In FIG. 1, 1 is a recording signal input terminal, 2 is a recording amplifier, 3 is a recording head, 4 is an erasure head, 5 is a bias and erasure signal oscillator, 6 is an output adjustment capacitor, 7 is a muting switch, 8 is a power supply switch to the oscillator 5.

These switches 7 and 8 are linked to each other, and a relay (not shown) is activated based on a control signal output from a system control circuit (not shown) in response to switching of a recording switch (not shown) of a tape recorder. ) are forced to open and close at predetermined timings.

In the above circuit, before the recording switch is closed, switch 7 is closed and switch 8 is open.

When the recording switch is closed in this state, a recording signal is applied from the input terminal 1 to the recording amplifier 2.

At this time, the switch 7 is opened with a delay of the time required for the recording amplifier 2 to start up, so during this time the output of the recording amplifier 2 flows to ground through the switch 7 and is muted.

On the other hand, when the switch 8 is closed and the 10B power supply voltage is supplied to the oscillator 5, its oscillation output is applied to the recording head 3 and erasing head 4.

When the recording amplifier 2 has sufficiently started up, the switch 7 is opened to cancel muting, and the output of the recording amplifier 2 is applied to the recording head 3.

As described above, in the past, recording switching was performed using a mechanical switch such as switch 7.8, which caused noise during switching and also caused problems in terms of reliability and economy.

This invention is intended to solve the above problem, and includes a transistor for muting the recording signal and a transistor for supplying power to the bias oscillator, and records the conduction and non-conduction of these transistors. Control is performed using a control signal obtained in response to switching.

An embodiment of the present invention will be described below with reference to FIG. 2, in which the same parts as in FIG. 1 are given the same reference numerals.

In FIG. 2, the collector of the muting NPN transistor 9 is connected to the input terminal of the recording amplifier 2, and the emitter is grounded.

The base is also connected to the power supply terminal 12 via resistors 10 and 11 to receive a 10B power supply.

On the other hand, the system control circuit 13 is configured to output a low level or high level control signal when a recording switch (not shown) of the tape recorder is switched.

This control signal is passed through a resistor 14 to an NPN for power supply.
It is applied to the base of the transistor 15 and also applied via the timing circuit 16 to the base of an NPN transistor 17 for muting control.

The collector of this transistor 17 is connected to the power supply terminal 12 via the resistor 11, and the emitter is grounded.

On the other hand, the collector of the transistor 15 is connected to the power supply terminal 12, and the emitter is connected to the power supply terminal of the oscillator 5.

Incidentally, when the recording switch (not shown) is closed and the tape recorder is set to the recording mode, the timing circuit 16 delays the high level control signal by approximately the same time as the rise time of the recording amplifier 2, and outputs the transistor. In addition to the 17 bases, when the above recording mode is canceled,
It is configured to pass low-level control signals without delay.

Next, the operation of the circuit with the above configuration will be explained.

Before the recording switch is closed, transistor 9 is in a conductive state and transistors 15 and 17 are in a non-conductive state.

If the recording switch is closed in this state, the recording amplifier 2
As soon as the signal starts to rise, a recording signal is applied to the input terminal 1.

This recording signal flows to ground through the collector-emitter of the transistor 9, which is in a conductive state, and is muted.

On the other hand, when the recording switch is closed, the system control circuit 13 outputs a control signal that rises from a low level to a high level.

This control signal is applied to timing circuit 16 and is also applied via resistor 14 to the base of transistor 15, causing transistor 15 to conduct.

As a result, the 10B power from the power supply terminal 12 is supplied to the oscillator 5 through the collector-emitter of the transistor 15, and the oscillator 5 is operated.

This oscillation output is applied to the erasing head 4 and also to the recording head 3 via the capacitor 6.

In this state, no recording signal is applied to the recording head 3 due to the muting operation of the transistor 9.

Next, when the recording amplifier 2 starts up sufficiently, the timing circuit 1
A control signal delayed at 6 is applied to the base of transistor 17, causing it to conduct.

As a result, the collector potential of this transistor 17 decreases, and the base potential of the transistor 9 connected to this collector decreases, so that this transistor 9 becomes non-conductive and muting is canceled.

Therefore, the recording signal is amplified to a predetermined level by the recording amplifier 2 and applied to the recording head 3, and recording is started.

Next, in the above state, when the recording switch is opened to stop recording, the output of the recording amplifier 2 begins to fall and the control signal from the system control circuit 13 immediately falls to a low level.

This low level control signal is applied directly to the base of transistor 17 without being delayed by timing circuit 16, causing transistor 17 to become non-conductive.

Therefore, the base potential of transistor 9 rises and transistor 9 becomes conductive again to mute the recording signal.

That is, since muting is applied almost simultaneously when recording is stopped, no recording signal is added to the fall time of the recording amplifier 2.

The low level control signal is also applied to the base of the transistor 15 via the resistor 14,
5 is rendered non-conductive, the supply of 10B power to the oscillator 15 is cut off, and the oscillator 15 stops operating.

According to the above operation, when the recording mode is set,
Muting is applied immediately, muting is canceled after recording amplifier 2 has sufficiently started up, and muting is applied almost simultaneously when recording is stopped and the recording amplifier starts to fall down, causing distortion on the magnetic tape. It is possible to prevent the recording signal from being recorded.

The above has described the case where muting is applied when switching recording, but by forcing the system control circuit 13 to output a control signal in response to the opening and closing of the power switch that supplies and cuts off the 10B power, the 10B It is also possible to apply muting at the rise and fall of the power supply voltage when switching between supplying and cutting off the power supply.

In the present invention, a first transistor 9 for muting the recording signal when switching recording is provided on the input side or output side of the recording amplifier 2, and a power terminal 12 is connected to the control electrode (base) of the first transistor 9. A second transistor 15 for supplying the power to the bias oscillator 5 is connected between the power supply terminal 12 and the bias oscillator 5 in response to the recording switching. The second transistor 15 is controlled based on the control signal obtained from the system control circuit 13 (the control signal obtained from the system control circuit 13), and the second transistor 15 is further delayed by a predetermined time from the output of the control signal when switching to recording. Timing circuits 16 and 17 are provided for rendering the first transistor 9 non-conductive and rendering the first transistor 9 conductive substantially simultaneously with the output of the control signal when recording is stopped. This relates to a recording switching circuit of a tape recorder.

Therefore, according to the present invention, since muting is applied for a predetermined period of time from the time of the recording start operation, a distorted signal due to the rise of the recording amplifier is not recorded.

Furthermore, since muting is applied almost simultaneously with the operation to stop recording, a distorted signal due to a falling edge of the recording amplifier will not be recorded.

Further, the timing circuit and bias oscillator for timing the muting can be controlled based on a common control signal obtained from the system control circuit.

In this case, regardless of muting, power is supplied to the bias oscillator at approximately the same time as the recording start operation, and the power can be cut off approximately at the same time as the recording stop operation.

Furthermore, since recording is changed by electronic switching, reliability is high and there are no problems such as generation of noise.

Furthermore, since bipolar transistors can be used as the two transistors, they can be manufactured at low cost.

[Brief explanation of drawings]

FIG. 1 is a circuit diagram showing a conventional recording switching circuit, and FIG. 2 is a circuit diagram showing an embodiment of the present invention. In the symbols used in the drawings, 2 is a recording amplifier, 3 is a recording head, 4 is an erase head, 5 is a bias oscillator, 9 is a muting transistor, 12 is a power supply terminal, 13 is a system control circuit, and 15 is a This is a power supply transistor.

Claims (1)

[Scope of utility model registration request] A first transistor for muting the recording signal at the time of recording switching is provided on the input side or output side of the recording amplifier, and power is supplied from the power supply terminal to the control electrode of the first transistor, and A second transistor for supplying the power to the bias oscillator is connected between the power supply terminal and the bias oscillator, and the second transistor is connected between the power supply terminal and the bias oscillator.
further controls the first transistor to be non-conducting after a predetermined time delay from the output of the control signal when switching to recording, and outputting the control signal when recording is stopped. A recording switching circuit for a tape recorder, comprising a timing circuit for rendering the first transistor conductive substantially simultaneously with the output.