JPS6141258A - Telephone set - Google Patents

Abstract

PURPOSE:To reduce the overall size of a telephone set without using specially a transformer, a battery, etc. by connecting a constant voltage element in series to a transmitter microphone to form a constant voltage power supply circuit, obtaining a power supply of an amplifier circuit for call signals received from a telephone circuit with the output of said constant voltage power supply circuit and at the same time applying muting to said amplifier circuit with the voltage emergizing at both ends of the transmitter microphone. CONSTITUTION:When connection terminals L1 and L2 are connected to a telephone circuit, the DC voltage which is usually equal to 48V and applied to the telephone circuit itself is applied directly to both terminals L1 and L2. Therefore an approximately constant DC voltage level emerges at both ends of a constant voltage element ZD regardless of a transmission or reception mode. This DC voltage is applied as the power supply voltage of an amplifier 11 and a muting circuit 13. Thus these amplifier 11 and the circuit 13 can be actuated without using any special power supply.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a telephone set called a speaker horn that uses a speaker to amplify a received signal.

Conventional configuration and its problems In a telephone set generally called a speakerphone, as shown in FIG. A signal is extracted through a transformer 2, amplified by an amplifier 4 driven by a separately provided power source 3, and applied to a speaker 5. However, this type of device requires a separate transformer 2 and power supply 3, which increases the size of the telephone as a whole.In addition, the signal from the transmitter 6 is transmitted through a hybrid transformer T and a resistor R1°R.
2, R13, R,, R5, capacitor 0. , 02. Although the sidetone prevention circuit consisting of varistors V, , V2, etc. is configured so that it does not appear significantly on the handset connection terminals S, B2, once the handset connection terminals S, B2, etc.
When the signal from the transmitter 6 appears in the transformer 2.b, this is transmitted to the transformer 2.b. Since it is greatly amplified by the amplifier 4 and applied to the speaker 5, a transmission sound that is louder than the speaker 5 appears, resulting in a problem that a large sidetone prevention effect cannot be obtained.

OBJECTS OF THE INVENTION The present invention eliminates the above-mentioned conventional drawbacks, and provides an excellent telephone that has a simple configuration, can be downsized, and can obtain a sufficient sidetone prevention effect. The purpose is to

Structure of the Invention The present invention connects a constant voltage element in series to a telephone transmitter, configures a constant voltage power supply circuit with this constant voltage element, and amplifies a reception signal from a telephone line by the output of this constant voltage power supply circuit. In addition to obtaining a power source for the amplifier circuit, the amplifier is configured to mute the amplifier at the time of transmitting a voice using the voltage appearing across the transmitter.

DESCRIPTION OF THE EMBODIMENT FIG. 2 is an electrical wiring diagram of an embodiment of the telephone according to the present invention. In the figure, L, R2 are connection terminals connected to the telephone line, and 10 is an hybrid transformer T3. Resistance R,
,,R,2,R13,R1,4,Capacitor CIl.

C,2,0,3,C,,,Barista■1. Well-structured telephone network.

11 is the third winding of the hybrid transformer T whose input end constitutes the telephone network 10! 12 is a speaker connected to the output terminal of the amplifier circuit 11 via a capacitor 019, and 13 is a transistor TR, TR2, TR3.
, resistors R1, to R26, and capacitors CI5 to CtS, it is a muting circuit that detects the voltage across the transmitter 14 and mutes the amplifier 11 when transmitting a voice.

The transmitter 14 is connected in series with a parallel circuit of a constant voltage element ZD such as a Zener diode and a capacitor C31, and an amplifier 11. The muting circuit 13 is configured to receive power from a constant voltage circuit comprising the constant voltage element ZD and capacitor C11. Further, the hybrid transformer T is the first one. Second. Third three windings -0
1, A2. Consists of A3, third winding! A capacitor CI4 is connected to the intermediate tap of , so that the reception signal is input to the amplifier 11 with stable impedance.

In the above embodiment, when the connection terminal R2 is connected to the telephone line, the normal 48V DC voltage applied to the telephone line itself is directly applied to the connection terminal.

Since it is applied to R2, a constant DC voltage appears at both ends of constant voltage element ZD regardless of whether a call is being sent or received. Since this DC voltage is applied as the power supply voltage to the amplifier 11 and the muting circuit 13, the amplifier 11 and the muting circuit 13 do not need to use a separate power supply.
can be made operational.

Now, if a reception signal is input through the telephone line, it will be applied from the connection terminal R2 to the amplifier 11 via the telephone circuit network 10, and will be amplified by the speaker 12.

On the other hand, when a signal is output from the transmitter 14, the muting circuit 13 is activated. That is, when the transmitter 14 outputs multiple signals, the voltage across them changes, which is amplified by the transistor TR, and is amplified by the capacitor CI? + applied to transistor TR2 through resistor R2o. Therefore, if the level of the signal output from the transmitter 14 is above a certain value, the transistor TR2 turns on and off, and the capacitor 018 is charged with a constant voltage. Therefore, the transistor TR3 is turned on by the charging voltage of the capacitor C78, and the amplifier 11 is muted. That is, the transmitter 1
When more than 4 signals are output, muting is applied to the amplifier 11, and the signal from the transmitter 14 is output to the speaker 1.
2 is prevented from being applied. Therefore, according to the embodiment described above, even if the telephone network 10 is configured relatively simply, it is possible to effectively obtain the sidetone prevention effect.

Effect of the invention As is clear from the above embodiments, the present invention is an amplifier.

The muting circuit is configured so that its power source is obtained from a constant voltage power supply circuit consisting of a constant voltage element connected in series with the transmitter.Therefore, no separate transformer or battery is required, and the telephone as a whole It has the advantage that it can be made considerably smaller. According to the present invention, the voltage across the transmitter is detected at the time of transmitting a call, and muting is applied to the amplification circuit that amplifies the received signal. This system has the advantage that it is possible to completely prevent the noise from appearing significantly in the stereophonic force, and that a sufficient sidetone prevention effect can be obtained even if the telephone circuit network is configured relatively simply.

[Brief explanation of drawings]

FIG. 1 is an electrical wiring diagram of a conventional telephone, and FIG. 2 is an electrical wiring diagram of an embodiment of the telephone of the present invention. 10... Telephone circuit network, 11 Amplifier, 12... Speaker, 13... Muting circuit, 14... Transmitter, ZD
... Constant voltage element, LI, L2 ... Telephone line connection terminal.

Claims (1)

[Claims] A constant voltage power supply circuit consisting of a constant voltage element that is connected in series to a transmitter connected to a telephone line and outputs a predetermined constant voltage, and the output from this constant voltage power supply circuit is used as a power supply,
It comprises an amplifier circuit that amplifies the received signal from the telephone line and drives a speaker, and a muting circuit that detects the voltage appearing across the transmitter during transmission and mutes the amplifier circuit. telephone.