JPH0391381A - Audio multiplex receiver - Google Patents

Abstract

PURPOSE:To keep the reception mode desired by a user in the state of dual audio reception by monitoring a voltage fed to an output mode setting terminal and keeping a voltage at a reception mode detection terminal forcibly to a 1st value when the monitored voltage is a 2nd voltage. CONSTITUTION:Suppose that the user desires a sub audio reception and selects a switch 23 to the position of a 2nd voltage, then even when a received electric field is weaker and a voltage at a terminal 14 is going to reach a 3rd value, since a holding circuit 30 keeps closing a switch 21, the terminal 14 keeps the 1st value. Since the circuit 30 has a hysteresis characteristic, even when the value of the terminal 14 may change, the output of the circuit 30 is not immediately changed. when the user selects only the output of a sub audio signal from output terminals 12, 13, the selection information is fed also to the reception mode detection terminal 14. Even when the voltage at the terminal 14 changes at a weak electric field or the like and the automatic changeover function is going to select a monaural output, the level of the terminal 14 is forcibly kept to the voltage (1st value) in the dual audio reception mode and not simply selected to the monaural output state caused in a conventional receiver.

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Industrial Field of Application) The present invention relates to an audio multiplex receiver that receives and processes audio multiplex broadcast signals transmitted through television broadcasting.

(Prior Art) A single-chip integrated audio multiplex signal demodulation circuit has been developed. This circuit also includes a complex filter, simplifying the circuitry around the chip.

FIG. 4 shows a conventional receiving device using such an integrated circuit, and an audio multiplex signal processing circuit 100 has an input terminal 11.
, an output terminal 12.13, a reception mode detection terminal 14 for identifying the mode of the currently input multiplexed signal, and an output setting terminal 15 for switching and setting the signal output to the output terminal 12.13. has.

The reception mode detection terminal 14 has a detection output of a first value when the duplex audio reception is on, a detection output of a second value larger than the first value when the monaural reception is on, and a detection output of a second value that is larger than the first value when in the stereo reception mode. A detected output voltage having a third value between the first value and the second value is obtained.

Furthermore, in the dual audio reception mode or the stereo reception mode, the audio multiplex signal processing circuit 100 selects the main audio signal of the dual audio signal when the voltage supplied to the output mode setting terminal 15 is the first voltage. Re-output terminal 12.13
When the second voltage is higher than the first voltage, the sub audio signal is output to the re-output terminal 12.13, and when the third voltage is between the first voltage and the second voltage, the sub audio signal is output to the re-output terminal 12.13. 1. Main and sub audio signals are output to second output terminals 12.13. moreover,
The audio multiplex signal processing circuit 100 has a built-in automatic mode switching function that automatically switches to the main audio signal output mode when the voltage at the reception mode detection terminal changes from the first value or the second value to the third value. There is.

FIG. 5 shows the output voltage of the reception mode detection terminal 14,
It shows the relationship with the mode of the input audio multiplex signal. In the dual audio reception mode, a detection output of the first value is obtained, in the stereo reception mode a detection output of the second value is obtained, and in the monaural reception mode a third detection output is obtained. Then, centering on the detection output of the third value, the first value or the second value
When changing to the value of , it is set to change with hysteresis characteristics.

Here, it is assumed that the stereo reception mode is in effect and the user is supplying the third voltage to the output mode setting terminal 15.

When the received radio waves are good, the output terminals 12 and 13 are connected to main (
R) and sub (L) audio signals can be obtained, but in a weak electric field or a receiving state with a lot of noise, the output voltage of the reception mode detection terminal 14 becomes the third value. Then, the automatic mode switching function is activated and the output mode is switched to a state in which only the main audio signal is output. In other words, the state is changed to outputting only the main (R) audio signal to the re-output terminals 12 and 13. Also,
When switching from this state to the original stereo reception mode, the device automatically switches to the stereo output state. In this way, when the radio wave condition is poor and the stereo output becomes harsh, the system switches to the monaural output state.

This function is the same in dual audio reception mode.

It is now assumed that Japanese is being broadcast primarily and a foreign language is being broadcast secondary, and a second voltage is being applied to terminal 15, for example. In other words, the user re-outputs the audio signal in a foreign language to the terminal 12.1.
Assume that you have obtained 3. In this state, if the radio wave condition deteriorates, the above circuit automatically switches to the main audio output state (monaural output state). Therefore, the output audio suddenly switches from a foreign language to Japanese. When the radio wave conditions improve from this state, the language will switch from Japanese to the foreign language.

(Problems to be Solved by the Invention) As mentioned above, in the conventional audio multiplex signal processing circuit, switching from a stereo reception state to a monaural reception state, or switching in the opposite direction, is not a problem for the user. However, frequent switching from a foreign language to Japanese, or vice versa, may make it difficult to understand the broadcast content.

In particular, in the case of a vehicle-mounted audio multiplex receiver, the radio wave conditions change frequently, so the switching of dual audio as described above is likely to occur.

SUMMARY OF THE INVENTION It is therefore an object of the present invention to provide an audio multiplex reception device that allows a user to maintain a desired reception mode, especially in a dual audio reception state.

[Configuration of the Invention (Means for Solving the Problems) This invention processes an input television audio multiplex signal, and processes the first.
a reception mode detection terminal having a second output terminal and for obtaining identification of the mode of the currently input multiplexed signal;
It has an output mode setting terminal that can switch and set the signals output to the first and second output terminals, and the reception mode detection terminal has a detection output of the first value when in the dual audio reception mode, a monaural reception In the stereo reception mode, a detection output voltage of a second value larger than the first value is obtained, and in the stereo reception mode, a detection output voltage of a third value between the first value and the second value is obtained. When in reception mode or stereo reception mode,
When the voltage supplied to the output mode setting terminal is the first voltage, the main audio signal of the dual audio signal is outputted to the re-output terminal, and when the voltage supplied to the output mode setting terminal is a second voltage larger than the first voltage, the sub audio signal is outputted. A signal is output to the re-output terminal, and when the third voltage is between the first voltage and the second voltage, the first . Main and sub audio signals are output to the second output terminal, and when the voltage at the receiving mode detection terminal changes from the first value or the second value to the third value, the main audio signal output mode is automatically switched. In the audio multiplex signal processing circuit that has a built-in switching function, the voltage supplied to the output mode setting terminal is monitored, and when the second voltage is applied to the output mode setting terminal, the receiving mode detection terminal is connected to the receiving mode detection terminal. means for forcibly maintaining the voltage at the first value.

(Function) As long as the output mode setting terminal is set to the second voltage by the above means, the reception mode detection terminal is maintained at the same value as when receiving dual audio, regardless of the actual reception state. Therefore, the internal automatic output mode switching function no longer switches to the monaural output state, and the sub-audio output state can be maintained as the output.

(Example) Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 shows an embodiment of the present invention. An audio signal separated from a television signal is supplied to an input terminal 11 of the audio multiplex signal processing circuit 100.

The audio multiplex signal is modulated using the FM-FM method.

The audio multiplex signal processing circuit 100 has output terminals 12 and 13 as explained in FIG. .13 has an output mode setting terminal 15 that can switch and set the output signal.

The reception mode detection terminal 14 has a detection output of the first value in the dual audio reception mode, and a detection output of the first value in the monaural reception mode.
In the stereo reception mode, a detected output voltage of a third value between the first value and the second value is obtained.

Further, this audio multiplex signal processing circuit 100 selects the main audio signal of the dual audio signal when the voltage supplied to the output mode setting terminal 15 is the first voltage in the dual audio reception mode or the stereo reception mode. When the second voltage is higher than the first voltage, the sub audio signal is output to the re-output terminal 12.13, and when the second voltage is higher than the first voltage, the sub-audio signal is output to the re-output terminal 12.13. 3 voltage, the 1st voltage. Main and sub audio signals are output to second output terminals 12.13. Furthermore, the audio multiplex signal processing circuit 100 has a built-in automatic mode switching function that automatically switches to the main audio signal output mode when the voltage of the reception mode detection terminal changes from the first value or the second value to the third value. are doing.

Next, in this system, switches 21 and 22 are connected in series to the reception mode detection terminal 14, and a holding circuit 30 is also connected thereto. The holding circuit 30 has a function of holding the voltage value of the reception mode detection terminal 14 at a first value (a value indicating the dual audio reception mode) and turning on the switch 21. The switch 22 is interlocked with a switch 23 connected to the output mode setting terminal 15. In other words, when the switch 23 is connected to the output mode setting terminal 15,
When the second voltage is set to be applied (set to the mode for outputting sub-audio to the output terminals 12 and 13), the terminal 2a of the switch 22 selects the terminal 2b,
The voltage value of the reception mode detection terminal 14 is forcibly maintained at the same value (first value) as when receiving the dual audio signal. In other output motos,
Be open.

The output terminal 3a of the switch 23 is connected to the output mode setting terminal 15, and the output terminal 3a of the switch 23 is connected to the output mode setting terminal 15.
voltage can be switched arbitrarily. Output terminal 12.1
3. When obtaining the main audio signal in both cases, the first voltage is selected and applied, and when obtaining the sub audio signal, the second voltage is selected and applied to obtain the main and sub audio signals to each terminal. In this case, a third voltage is applied. These voltages are connected to the voltage source EO
and a voltage dividing resistor RISR2.

Assume that a dual audio signal is now being received in the above circuit. Here, the user desires sub-audio as the audio signal output to the output terminal 12.13, and selects the switch 23.
It is assumed that the voltage is switched to the second voltage side. In the dual audio signal reception mode, the voltage at the reception mode detection terminal 14 takes the first value as shown in FIG. This value is
It is held by the holding circuit 30, and the switch 21 is turned on by this held value. As a result, the first value (ground potential) is applied to the terminal 14 from inside and outside.

Here, even if the received electric field weakens and the value of the terminal 14 is about to reach the third value, the holding circuit 30 continues to turn on the switch 21, so the terminal 14 maintains the first value. .

Since the holding circuit 30 has hysteresis characteristics, the terminal 1
Even if the value of 4 changes, the output of the holding circuit 30 does not change immediately).

In this manner, when the user selects only the output of the sub audio signal from the output terminals 12 and 13, the selection information is also transmitted to the reception mode detection terminal 14 side. and,
If the voltage at the detection terminal 14 changes due to a weak electric field, etc., and the automatic switching function attempts to switch one monaural output, the terminal 14
The potential is maintained at the voltage (first value) of the forced single-duplex audio reception mode, and is not easily switched to the monaural output state as in the conventional case.

FIG. 2 is a circuit diagram showing the first circuit in more detail. The holding circuit 30 includes an innocent 301 to which the output of the reception mode detection terminal 14 is supplied, a diode 302 that integrates this output, and a capacitor 303.
, a buffer amplifier 304 to which this integrated output is supplied, and a discharge resistor 305. Further, a bidirectional semiconductor switch 211 is used as the switch 21,
The switch 23 includes a Zener diode 221 and a resistor 22.
2. Consists of an inverter 223.

When a voltage of the first value is obtained at the reception mode detection terminal 14, the charging voltage is accumulated in the integrating circuit in the holding circuit 30, and the switch 21 is made conductive.

In this state, even if the potential of the reception mode detection terminal 14 changes, the output of the holding circuit 30 does not change immediately. The time it takes to obtain this change is the capacitor 30
3 and the time constant of the resistor 305. On the other hand, the switch 23 is set to output the second voltage (state shown)
When the diode 221 is turned off, the inverter 22
3 outputs a high level (first value), and this potential is applied to the terminal 14 through the switch 211.

Figure 3 shows the operation of the audio multiplex signal processing circuit 3. FIG. 3 is a diagram showing waveforms.

+611fi (A) indicates the input signal level, and CB in the same figure
) indicates the potential of the reception mode detection terminal 14.

FIG. 2C shows the state of audio output by the conventional circuit. In the conventional circuit, the sub audio output state changes to the main audio output state each time the potential of the reception mode detection terminal 14 reaches the third value. However, according to the circuit of this example,
The output of the holding circuit 30 changes as shown in (D) in the same figure, and in order to prevent the potential of the reception mode detection terminal 14 from changing immediately (see (E) in the same figure), the audio output state changes as shown in (F) in the same figure.
The sub-audio output state is maintained as shown in FIG.

[Effects of the Invention] As described above, according to the present invention, it is possible to maintain the reception level desired by the user, especially in the dual audio reception state.

[Brief explanation of drawings]

FIG. 1 is a circuit diagram showing an embodiment of the present invention, FIG. 2 is a circuit diagram showing the circuit of FIG. 1 in more detail, and FIG. 3 is a circuit diagram for explaining the operation of the circuit of the present invention. FIG. 4 is a block diagram showing a conventional audio multiplex receiver, and FIG. 5 is a diagram showing output voltage characteristics of a reception mode detection terminal. 12.13... Audio output terminal, 14... Reception mode detection terminal, 15... Output mode setting terminal, 21.22
．． 23...Switch, 30...Holding circuit.

Claims (1)

[Scope of Claims] A reception mode detection terminal for processing an input television audio multiplex signal, having first and second output terminals, and for obtaining identification of the mode of the multiplex signal currently being input; It has an output mode setting terminal that can switch and set the signal output to the first and second output terminals, and the reception mode detection terminal has a detection output of the first value in the dual audio reception mode, a detection output of the first value in the monaural reception mode When the detection output voltage is a second value larger than the first value, and in the stereo reception mode, the detection output voltage is a third value between the first value and the second value, and dual audio reception is performed. mode or stereo reception mode, when the voltage supplied to the output mode setting terminal is the first voltage, the main audio signal of the dual audio signal is output to both output terminals, and the first
When the second voltage is greater than the voltage, the sub audio signal is output to both output terminals, and when the third voltage is between the first voltage and the second voltage, the main audio signal is output to the first and second output terminals. , a sub-audio signal is output, and the voltage of the reception mode detection terminal is a first value or a second value.
In the audio multiplex signal processing circuit, which has a built-in function of automatically switching to the main audio signal output mode when the value changes from the value to the third value, the voltage supplied to the output mode setting terminal is monitored, and this output mode setting is performed. An audio multiplex reception device characterized by comprising means for forcibly maintaining the voltage of the reception mode detection terminal at the first value when the second voltage is applied to the terminal.