JPS5823986B2 - Variable volume telephone - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a telephone with a variable listening volume that allows the listening volume to be adjusted by operating a switch.

When a hearing-impaired person speaks on a telephone, the hearing loss in the ear is large, so the listening volume must be increased by the amount of loss, and the volume needs to be 20 to 30 dB higher than the volume of a normal person.

Additionally, in general, telephones are not only used exclusively by people with hearing loss, but also so-called normal people (people with normal hearing) who have no hearing problems, so it is necessary to make it easy for both parties to use them.

Conventionally, such switching has been carried out as disclosed in Japanese Patent Application Laid-Open No. 133710/1983, a book diagram of which is shown in FIG. 1, and a specific example is shown in FIG.

In this conventional method, when switching between a hearing-impaired person and a normal person, the amount of change in input impedance is large;
There is a drawback that it causes the balance of the balanced circuit of the telephone connected in parallel to be disturbed.

To this end, the secondary side of the transformer 8 is terminated with a fixed resistor 9 to suppress the amount of change in impedance, but this has the drawback of causing a loss of 3 dB at the input section.

The present invention improves the shortcomings of these circuits and provides a variable volume telephone that is compact and capable of reducing input impedance changes and losses through simple control and making stable, high-quality calls.

The present invention will be explained in detail below.

Figures 3.4.5 show specific examples of the present invention, and each will be explained below.

Referring to FIG. 3, the flip-flop circuit 17 is initially in a normal state and the output Q is at a low level.

At this time, the transistor 13 is turned off, and the input signal from IN is attenuated by the voltage division ratio determined by the first and second fixed resistors 19 and 21 through the transformer 8 and the third fixed resistor 21. The attenuation amount for a normal person is set by two of the attenuation amounts determined between the input impedance of the receiver amplifier 14, and the attenuation amount is amplified by the amplifier 14 to drive the receiver 16.

This is the first signal input path. In the case of a hearing-impaired person, the flip-flop circuit 17 is inverted under the control of the control switch S, the transistor 13 is turned on, and the receiver 16 is driven through the receiver amplifier 14 by the attenuation amount determined by the variable resistor 23. (This is the second signal input path) to obtain a level difference of 20 to 30 dB between a normal person and a hearing-impaired person.

By setting the fixed resistor 20 to be larger than the secondary impedance of the transformer 8, there is no effect of attenuation on the other party due to switching between a normal person and a hearing-impaired person.

In this specific example, by using the amplifier 14 when its input impedance is larger than the secondary impedance of the transformer 8, changes in the secondary impedance of the transformer 8 and loss can be extremely reduced.

In Figure 4, the first and second levels are used to set the level of a normal person.
This is simplified by replacing one of the fixed resistors with a variable resistor 25, and the operation is the same as that shown in FIG. Use when is large.

In addition, in FIGS. 3 and 4, if the input impedance of the amplifier 14 is small and if the variable resistors 23 and 25
If the attenuation at the amplifier 14 is set to the minimum, the transformer 8 will be greatly affected by the input impedance of the amplifier 14, but FIG. 5 shows a circuit configuration that further solves this problem. This is a specific example where the input impedance of the amplifier 14 is smaller than the secondary impedance of the transformer 8.

In the case of a normal person (person with normal hearing), the flip-flop circuit 17
is the initial state, and the output Q is at a low level, that is, the transistor 34, which is the output active element, is in the on state.

Using this, one side of the fixed resistor 30 is connected to the capacitor 31.
By connecting the fixed resistor 30 to the output Q of the flip-flop circuit 17, one side of the fixed resistor 30 is grounded in an alternating current manner, and the attenuation amount for a normal person is set at the fixed resistor 28°29.30.

At this time, the secondary side of the transformer 8 is connected to a fixed resistor 28 on the AC side.
．． It will be terminated at 30.

In the case of a hearing-impaired person, the flip-flop circuit 17 is inverted under the control of the control switch S, the transistor 34 is turned off, and at the same time the transistor 13 is turned on, and a fixed resistor 28 is connected to the secondary side of the transformer 8. A variable resistor 32 and a fixed resistor 33 are included together with the resistor 28.

The input impedance of the amplifier 14 is low and the fixed resistor 1
5 is also connected in parallel, but overall the change in impedance connected to the secondary side of the transformer 8 is reduced.

In this way, without increasing the number of active elements compared to the conventional circuits shown in Figs. 1 and 2, even in a receiver amplifier with low input impedance, the change in input impedance with respect to the input signal source is small and there is little loss. A circuit can be constructed.

FIG. 6 shows an example of the flip-flop circuit 17 controlled by the control switch S.

Since the operation can be understood from the above explanation, detailed explanation will be omitted.

As described above, the variable listening volume telephone set of the present invention has the advantage that loss can be reduced without disturbing the balance of the telephone circuit network, and the listening volume can be varied with a simple switch structure and control.

[Brief explanation of drawings]

1 and 2 are block diagrams and circuit diagrams showing a conventional example, FIGS. 3, 4, and 5 are circuit diagrams showing an embodiment of the present invention, and FIG. 6 is a flip-flop used in the present invention. FIG. 2 is a circuit diagram showing an example of a circuit.

Claims (1)

[Claims] 1 The input signal is voltage-divided by a first resistance element and a second resistance element connected in parallel to the signal source, and a third resistance is connected between the voltage-divided point and the input terminal of the receiving amplifier. The elements are connected to form a first signal input path, and the first resistance element or the second resistance element is used as a variable resistance element, or the first resistance element and the second resistance element are connected in series or in parallel. A variable resistance element is connected, and a switch means is provided between the variable output terminal of the variable resistance element and the input terminal of the receiver amplifier to form a second signal input path, and the on/off control of the switch means causes the the first signal input path or the second signal input path;
A telephone with a variable reception volume configured to select a signal input path of the input signal to control an amount of attenuation of a signal applied from the signal source to the reception amplifier.