JPH02301355A - Side tone control circuit for digital telephone set - Google Patents

Abstract

PURPOSE:To apply switching control to the adjustment of side tone and the adjustment of sound volume at the same time by connecting other terminal of the side tone circuit in one switching state and a receiver via a sound volume adjustment circuit between the receiver output terminal and the receiver, interrupting the side tone circuit in the other switching state and short-circuiting the sound volume adjustment circuit. CONSTITUTION:When a communication opposite party is a digital line, a sound volume adjustment circuit 13 outputs a transmission signal outputted from a CODEC 10 to a line 15 connecting to a receiver through the sound volume adjustment circuit 13. On the other hand, one terminal of the side tone circuit 11 connects to the line 14 and the other terminal connects to the line 15 via a sound volume switching circuit 12, a transmission signal generated in a transmitter is inputted to the CODEC 10 and fed to the receiver as a side tone through the side tone circuit 11 at the same time. In the case of communication with the opposite party of the analog line, when the sound volume switching circuit 12 is switched to the inverted state and the side tone circuit 11 is interrupted and the sound volume adjustment circuit 13 is short- circuited. Thus, the switching of the received sound volume is switched without provision of the side tone changeover switch and the side tone is controlled.

Description

[Detailed Description of the Invention] [Summary] Regarding the sidetone control circuit of a digital telephone provided between the transmitter/receiver and the coder/decoder circuit, a digital telephone that can simultaneously switch and control sidetone adjustment and volume adjustment in the digital telephone is provided. The purpose of this circuit is to provide a sidetone control circuit for telephones, with a sidetone circuit whose one end is connected to a line that connects to a transmitter, and a sound 1 circuit that is provided between the receiving output terminal of the encoding/decoding circuit and the receiver. ! The volume switching circuit includes a volume adjustment circuit, the other end of the sidetone circuit, and two terminals connected to both ends of the volume adjustment circuit, and the volume switching circuit is configured to switch the other end of the sidetone circuit in one switching state. The terminal and the receiver are connected, and the receiver output terminal and the receiver are connected via a volume adjustment circuit, and in the other switched state, the sidetone circuit is disconnected and the volume adjustment circuit is short-circuited.

[Field of Industrial Application] The present invention relates to a sidetone control circuit for a digital telephone provided between a transmitter/receiver and an encoder/decoder circuit.

In recent years, along with the digitization of telephone exchanges, the digitization of telephones has been progressing. Digital telephones communicate through a so-called four-wire line in which lines for sending and receiving calls are separated.

On the other hand, as a function of telephones, it has traditionally been required to generate sidetone by returning a portion of the transmitted signal to the handset side in order to have a natural-sounding conversation.

Conventional analog telephones use two wires for transmission and reception, which naturally generates side noise, but digital telephones have four wires, so they have to connect the transmitting line with the transmission line to generate side noise. A sidetone circuit is provided between the receiving line.

However, even if the exchange that houses the digital telephone is a digital type, telephone calls are made not only with parties housed in the same exchange, but also with parties housed in other exchanges through trunk lines. . In this case, if the destination to which the call is made is an analog line, sidetone occurs even in the trunk that performs 4-to-2 line conversion, making it difficult to make a good call, and improvements are desired.

[Prior Art] Fig. 3 is a connection system diagram of an exchange system, Fig. 4 is an explanatory diagram of the relationship between side volume and receiving volume by line/distance, and Fig. 5 is a conventional side sound control circuit diagram.

In FIG. 3, 30 is a digital telephone, 31 is a digital exchange, 32 is a digital line interface (indicated by IF), 33 is an analog line trunk (indicated by TR), 34 is an analog exchange, and 35 is an analog telephone.

Regarding the configuration of this exchange system, for example, it is possible to specifically consider a case where the digital exchange 31 is a private branch exchange and the analog exchange 34 is a public telephone network exchange.

A digital telephone 30, shown as a representative of a large number of telephones housed in the digital exchange a31, is connected to the digital exchange 1131 by four wires with separate transmitting and receiving signals.

Between the digital telephone 30 and the digital exchange 31,
As has been known in the past, in the case of a communication system compatible with l5DN (Integrated Service Digital Network), 2B+D (
A communication path (two channels for information signals and one channel for control signals) is formed. An interface (indicated by IF) 301 within the digital telephone 30 controls the SDN protocol and channel multiplexing and demultiplexing.

The audio digital signal is subjected to A-D conversion (encoding and D-A (decoding)) in a codec (displayed by CODEC) 302, and the received signal becomes an analog signal and is supplied to the receiver 304, and the transmitter The analog signal sent from the codec 303 is converted into a digital signal by the codec 302 and supplied to the interface 301 .

When making a call from the digital telephone 30, both the outgoing and incoming calls are connected via the digital exchange 31, and if the other party is on the same extension line of the digital exchange 31, or the other party is connected to a trunk line of the digital exchange (not shown). In this case, for example, a connection path (indicated by ■) with the interface 32 connected to a digital line (4 lines) is formed.

If the destination of the call is an analog line, the analog line trunk 33. A connection is made to an analog telephone 35 via an analog line and an analog exchange 34. FIG. 5 is a sidetone control circuit diagram of a conventional digital telephone.

That is, the codec 302 and the transmitter 303 in the digital telephone 30 in FIG. The arrangement between handsets 304 is shown in FIG.

In FIG. 5, an analog signal from a telephone receiver is input to an input terminal of a codec 301, and a reception signal outputted from an output terminal is amplified by an amplifier 55 via resistors 52 and 53 and supplied to the telephone receiver.

Resistor 54 is for feedback of amplifier 55.

Since digital telephones do not have a two-wire configuration like analog telephones, sidetone does not occur naturally. Therefore, in order to give a natural feeling, the transmitting signal generated from the transmitter is transferred to the receiving signal via the sidetone circuit 50. I am typing on the line. This sidetone is given to the handset together with the transmission signal, allowing the person speaking on the telephone to hear his or her own voice through the handset.

Also, in Fig. 5, °ζ, switch (indicated by SW) 51
When the received volume becomes low, this switch switches from the state shown in the figure to short-circuit the volume adjustment resistor 53 to increase the volume. Furthermore, it is also used when the sidetone becomes louder than the volume, by changing the switch from the illustrated state to increase the call volume relative to the sidetone.

FIG. 4 is an explanatory diagram of the relationship between the side volume and the received volume by distance.

"Digital" and "Analog" shown in the "Line type" column in Figure 4 indicate whether the call destination of the digital telephone is a digital line or an analog line.In the example of Figure 3, the call destination is If the line is a digital line, the destination of the call to the digital telephone 30 is connected to the digital line via the interface 32. The route marked ■ extending to the analog telephone 35 corresponds to j.

In the case of a digital phone, the side volume is a constant value depending on the value of the side volume lB50 (actually constructed from a resistor) shown in the configuration of FIG. However, when the line type is analog, a 2-wire 4-wire conversion circuit (consisting of a hybrid transformer, etc.) provided in the analog line trunk 33 converts the transmission signal from the digital telephone 30 (
Sidetone occurs due to the phenomenon in which the signal passing through the path (2) wraps around the received signal. The received signal is input to the digital telephone 30 as a received signal through the route (3).

Therefore, in the case of the analog line type shown in Figure 4, the sidetone is small when the distance is short, but the sidetone becomes relatively loud when the distance is long. Since the sound volume is attenuated by the distance, it becomes smaller at a long distance.

[Problems to be Solved by the Invention] When the values of the side volume and listening volume shown in FIG. 4 above were adjusted using the conventional side sound control circuit shown in FIG. 5 when an analog line was used as the destination of the call. .

In that case, the resistor 53 for volume adjustment shown in FIG.
1, the volume is increased and the sidetone ratio is relatively lowered, thereby increasing the speech signal.

However, with this, the analog line trunk (Fig. 3 33)
There has been a problem in that the sidetone generated by the telephone and the sidetone from the sidetone circuit of the telephone are synthesized, causing distortion in the sidetone heard from the receiver, making it difficult to hear.

SUMMARY OF THE INVENTION An object of the present invention is to provide a sidetone control circuit for a digital telephone that can simultaneously switch and control sidetone adjustment and volume adjustment within the digital telephone.

[Means to solve the problem] FIG. 1 is a diagram showing the basic configuration of the present invention.

In FIG. 1, 10 is a codec, 11 is a sidetone circuit,
12 is a volume switching circuit, 13 is a volume adjustment circuit, 14 is a line connected to a transmitter, and 15 is a line connected to a receiver.

The present invention controls the insertion and disconnection of the sidetone circuit in conjunction with the switching control of the reception volume between high and low levels using a volume switching circuit.

[Operation] When the destination of the call is a digital line, the volume switching circuit 12 is manually operated to the illustrated state Li (connected to the upper side).

In this case, the volume adjustment circuit 13 outputs the transmission signal output from the codec 10 to the line 15 connected to the receiver through the volume adjustment circuit 13. Therefore, the received signal is adjusted (attenuated) by a predetermined volume.

On the other hand, at this time, one terminal of the sidetone circuit 11 is connected to the line 14, and the other end is connected to the line 15 via the volume switching circuit 12, so that the transmission signal generated by the transmitter is transmitted to the codec lO
At the same time as the signal is input to the receiver, it passes through the sidetone circuit 11 and is supplied to the receiver as sidetone.

When you use this digital telephone to make a call to the other end of an analog line, the call volume will be low, so you can switch the volume to 0 or 1.
2 in the opposite state from the one shown (connected to the bottom)
Switch to Then, the sidetone circuit 11 is disconnected and the sound N adjustment circuit 13 is short-circuited.

This switching prevents sidetone from occurring within the digital telephone, and at the same time, the volume adjustment circuit stops working, making it possible to increase the volume.

[Example] FIG. 2 is a configuration diagram of an embodiment.

In FIG. 2, 21 is a codec, 22 is a resistor that determines the side volume, 23 is a receiver volume changeover switch, 24 is a resistor that determines the increase lid for the receiver volume, and 25 is a resistor that determines the standard receiver volume. Resistor, 26 is a feedback resistor of the operational amplifier, 27 is an operational amplifier, 28 is a transmitter, 29
represents a handset.

To explain the operation of the embodiment, assuming that the receiving volume changeover switch 23 is currently in the upper position, the input resistance of the receiving human power of the operational amplifier 27 is the sum of the resistors 24 and 25, and the receiving volume is determined by the sum of this sum and the feedback. Determined by JI and anti-26. On the other hand, in this state, the sidetone is between resistance 22 and resistance 2.
6, and a predetermined level of sidetone determined in advance is supplied to the receiver 29.

Here, if you switch the listening volume selector switch 23 to the lower side,
The resistor 25 is short-circuited, and the only input resistance for the receiver's power of the operational amplifier 27 is the resistor 24, so that the gain of the receiver increases and the volume increases. On the other hand, at this time, the path from the transmitter 28 to the operational amplifier 27 is cut off, and no sidetone is generated. However, since this state is switched when the destination of the call is an analog line, the sidetone from the analog line trunk is returned, so only that sidetone is supplied to the handset.

[Effects of the Invention] According to the present invention, it is possible to switch the listening volume and control the sidetone without providing a sidetone changeover switch, thereby improving the operability of the telephone.

[Brief explanation of drawings]

Figure 1 is a diagram showing the principle configuration of the present invention, Figure 2 is a diagram showing the configuration of an embodiment,
Figure 3 is a connection diagram of the switching system, Figure 4 is a diagram of the line and
FIG. 5, which is an explanatory diagram of the relationship between the side volume and the listening volume according to distance, is a side sound control circuit diagram of a conventional digital telephone. In Figure 1, lO: Codec II: Sidetone circuit 12: Volume switching circuit 13: Volume adjustment circuit 14: Line connected to the transmitter 15: Line connected to the receiver Patent applicant Tomitsu Co., Ltd. Name) Kazuo Hosaka, sub-agent patent attorney

Claims (1)

[Claims] In a sidetone control circuit of a digital telephone provided between a transmitter/receiver and an encoder/decoder circuit, a sidetone circuit (11) whose one end is connected to a line (14) connected to the transmitter. , a volume adjustment circuit (13) provided between the receiving output terminal of the encoding/decoding circuit and the handset, and two terminals connected to the other end of the sidetone circuit (11) and both ends of the volume adjustment circuit. The volume switching circuit (12) is configured to connect the other end of the sidetone circuit (11) and the handset in one switching state, and control the volume between the receiving output terminal and the handset. A sidetone control circuit for a digital telephone, characterized in that a connection is made via an adjustment circuit (13), and in the other switching state, the sidetone circuit (11) is disconnected and the volume adjustment circuit (13) is short-circuited.