JPH0129102B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for controlling the volume of a slave station speaker in a wireless system.

Conventionally, in broadcast radio telephone systems installed in each municipality, the master station selects the target slave station with a selective call signal and controls the connection of the slave station speaker, but emergency broadcasts, especially in times of disaster, require the use of the loudspeaker. Regardless of the adjustment position of the volume adjustment variable resistor (hereinafter referred to as variable resistor), a system is adopted in which the notification is made at the maximum volume (forced volume). When a slave station receives a report at a forced volume, the following method has been used to cancel the forced volume state and receive the call at an appropriate volume, depending on the circumstances of the slave station. There are ways to detect induced electricity from a commercial power source through a variable resistor knob, and cancel the forced volume just by touching the knob, and how to cancel the forced volume by using a variable resistor with a switch. A method of turning off this switch has been adopted. In the former case, it will not be possible to operate during a power outage, and operation will become unstable depending on the connection between the power cord and the outlet. In the latter case, to cancel the forced volume and return to normal volume,
After turning the variable resistor switch to the off position, it is necessary to return it to the appropriate volume, which is cumbersome to operate. Further, if the variable resistor is left in the switch-off position, there are problems such as the forced volume not being broadcast.

In order to eliminate these drawbacks, the present invention applies a constant DC voltage to the input terminal of a variable resistor, detects a change in DC voltage by slightly rotating the knob of the variable resistor to the left, and uses this detection signal. This resets the forced volume circuit during emergency broadcasts.

FIG. 1 is a block diagram of a slave station audio circuit showing an embodiment of the present invention, in which 1 is an input terminal from a receiver;
2 is a selective call circuit, 3 is an output when a forced volume signal is received, and register 4 is set. 5 turns on the analog switch 6 with the output of the register 4, and connects the audio input from the input terminal 1 to the output amplifier 7. The other output 8 of the selective call circuit 2 controls the connection/disconnection of the speaker 10, and operates the output amplifier 7 to amplify the outputs of the analog switches 6 and 9, thereby driving the speaker 10. In normal broadcast,
Since the output 11 of the register 4 turns on the analog switch 9 and turns off the analog switch 6, the audio input is controlled to an appropriate volume by the variable resistor 12 and broadcast. A DC constant voltage source is connected to the terminal 14, and a detection circuit 15 detects a drop in DC voltage when the variable resistor 12 is turned counterclockwise, and its output 16 resets the register 4.
Therefore, when broadcasting at a forced volume, the volume signal is connected by the analog switch 6 and broadcasted at the maximum volume, but by turning the variable resistor 12 counterclockwise by approximately 10 degrees, the analog Switch 6 is turned off, analog switch 9 is turned on, and the volume can be adjusted to an appropriate level. 13 is a capacitor for DC leakage and is connected to input terminal 1.
If the audio signal has a stable DC bias, omit the DC constant voltage source at terminal 14 and connect it to terminal 1.
The output of the variable resistor 12 may be directly connected to the variable resistor 12.
Note that this method can operate correctly in the same state for the next received forced volume signal.

FIG. 2 is a circuit diagram showing details of the detection circuit 15. 18 is an output obtained by smoothing the audio signal and is constant regardless of the strength of the audio. The output voltage 18 is held at the terminal 19 as it is. 20 is an operational amplifier, and if the input impedance seen from the input terminal 18 to the operational amplifier side is sufficiently high, the output voltage 18 will be equal to the output impedance of the variable resistor and R ₁ and C ₁ in response to changes in the DC voltage at the input terminal 17. Although it changes with a time constant, since the potential of the terminal 19 is maintained at the previous state, the voltage difference between them is amplified and appears at the output terminal 21. This output 16 is used as a register reset signal.

As described above, according to the present invention, the forced volume cancellation function can be realized stably and inexpensively. When the volume is too high, turning the volume knob to the left is a natural behavior and is easy to operate. This method can also be effectively applied to the volume control circuit of a slave station in a voice calling wireless system.

[Brief explanation of drawings]

FIG. 1 is a block diagram of a slave station audio circuit showing an embodiment of the present invention, and FIG. 2 is a detailed circuit diagram of its detection circuit. 2: Selective call circuit, 4: Forced volume register,
6, 9: Analog switch, 7: Output amplifier, 1
2: Variable resistor for volume adjustment, 15: Detection circuit, 2
0: Operational amplifier.

Claims (1)

[Claims] 1 During normal broadcasting from the master station, a selective call signal is used to control the connection of the speaker of the target slave station, and the volume can be adjusted using a variable resistor for adjusting the volume of the slave station, and during emergency broadcasts, a forced volume signal is sent to the selective call signal. In addition, in a wireless system that forcibly maximizes the volume of the speaker of a slave station, direct current is applied to the input terminal of the volume adjustment variable resistor as a means for the slave station to receive at an appropriate volume during emergency broadcasts. A constant voltage source is connected to the output terminal, and a DC voltage detection circuit is connected to the output terminal, and the DC voltage change that occurs when the knob of the volume adjustment variable resistor is turned counterclockwise is detected by the DC voltage detection circuit, and this detection signal is detected. A speaker volume control method for a wireless system, characterized in that a forced volume circuit is reset by an emergency broadcast.