JPS59230355A - Hand-free talking device - Google Patents

Abstract

PURPOSE:To ensure the reception switching performance even with large external noise by detecting a mean value of a constant time of a signal for transmission system and reception system and allowing this output to control reciprocatingly a gain of a gain expanding circuit and a gain compressing circuit provided to the transmission system and the reception system. CONSTITUTION:A reception signal is inputted to a talking line 13, and after the signal is amplified by a gain of the gain compressing circuit 18 via a side tone proof circuit 12, a loss amount contrary to that of a variable loss circuit 4 is outputted from a comparator 10 via an inverter 11 and becomes an output of the reception system 6. The gain of the gain expanding circuit 17 and the gain compressing circuit 19 is controlled reciprocatingly in this case by controlling the loss amount of variable loss circuits 4, 8 so as not to generate ring tone based on the output of the comparator 10, controlling a switching circuit 16 and allowing a gain control circuit 19 to select which output of either a detecting circuit 14 or 15 detecting the mean value for a constant time. Thus, even if the ratio of external noise is increased resultingly, when the output of the detection circuit 14 is small, an accurate reception interrupting performance is obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a so-called hands-free type communication device that transmits speech using a microphone and receives amplified sound using a speaker.

Conventional configuration and its problems Page 2 Generally, a hands-free type communication device is configured as shown in FIG. In Fig. 1, ■ is a microphone used when transmitting a call, 2 is a transmitting system equipped with microphone 1, 3 is an amplifier inserted in the transmitting system 2, 4 is a variable loss circuit, and 5 is a speaker used when receiving a call. , 6 is a receiving system equipped with a speaker 5, 7 is an amplifier inserted in the receiving system 6, 8 is a variable loss circuit, 9 inputs the signal of the transmitting system 2 and the signal of the receiving system 6, and calculates the ratio of the power of both people. A comparison circuit that outputs a signal according to
10 is a comparator that compares the output of the comparison circuit 9 with a preset setting value T and outputs a signal according to the comparison value. 11 is an inverter. 12 is a communication line for transmitting the signal from the transmitting system 2. 1
3, and transmits the signal from the communication line 13 to the receiver system 6.

In the conventional communication device shown in FIG. 1, when transmitting a call, the ratio ST/SR between the signal ST of the transmitting system 2 and the signal SR of the receiving system 6 is relatively large. A signal with a value larger than the set value T is output. Therefore, a positive signal is also output to the output terminal of the comparator 1o, and this button controls the variable loss circuit 3 so that the loss of the page circuit 4 is reduced. Since the output of the comparator 10 is further applied to the variable loss circuit 8 via the inverter 11, the variable loss circuit 8 is controlled to increase its loss.

On the other hand, when receiving a call, the ratio ST/SR between the signal ST of the transmitting system 2 and the signal SR of the receiving system 6 becomes relatively small, so the output terminal of the comparator circuit 9 receives a signal with a value smaller than the preset value T. is output, and a negative signal is output to the output terminal of the comparator 10. Therefore, in this case, the loss of the variable loss circuit 4 is increased and the loss of the variable loss circuit 8 is controlled to be decreased.

In this way, even in conventional communication devices, the signals of the transmitting system 2 and the signals of the receiving system 6 are compared, and based on the results, variable loss circuits 4 and 8 are inserted into the transmitting system 2 and the receiving system 6, respectively. It is configured to reciprocally vary the loss of the noise, so normal operation can always be expected in low-noise conditions. However, as shown in Fig. 1, the signals of the transmitting system 2 and the receiving system 6 are simply compared, and the loss 1N of the variable loss circuit 4.8 is reciprocally varied based on the result. In a case where the signal from the transmitting side appears in the receiving system 6 as a sidetone of the side sound protection circuit 12 when transmitting, and when the ratio of ambient noise to the transmitted signal is large, the signal from the transmitting side appears on the communication line 13. Since the signal-to-noise ratio with the human power of the receiver deteriorates, the ability to determine the level of the received signal becomes poor, resulting in poor call switching performance compared to when there is little ambient noise, which has the disadvantage of degrading the quality of the call.

Purpose of the Invention The present invention eliminates the above-mentioned drawbacks of the conventional technology.It has a simple configuration, can ensure sufficient call switching performance even when the ratio of external noise is large, and has an S
It is an object of the present invention to provide an excellent hands-free communication device that can significantly improve the /N.

Structure of the Invention The present invention provides a variable loss circuit in each of the transmitting system and the receiving system, compares the signals of the transmitting system and the receiving system, and based on the results, changes the transmission system when transmitting and the receiving system when receiving. The variable loss circuit is configured to have a small loss of 51 degrees, and detection means for detecting the fixed time average value of the transmitting system signal and the fixed time average value of the receiving system signal are separately provided. The gain of the gain expansion circuit and the gain compression circuit inserted in the transmitting system and the receiving system are reciprocally controlled by the output of the means.

DESCRIPTION OF THE EMBODIMENT FIG. 2 is a block diagram of an embodiment of the hands-free communication device of the present invention, and the same reference numerals as in FIG. 1 indicate the same components as in FIG. 1. Detection circuits 14 and 15 detect fixed-time average values of the signals of the transmitting system 2 and the receiving system 6, respectively; and 16 is switched and controlled by the output of the comparator 10, and when transmitting, the detection circuits 14.
A switching circuit that outputs 15 outputs.

19 is a transmitting system 2 which inputs the output of the switching circuit 16;
This is a gain control circuit that reciprocally controls the gain compression circuit 17 and gain expansion circuit 18 inserted in the receiver system 6, respectively, as shown in FIGS. 3(a) and 3(b).

Incidentally, the detection circuits 14 and 15 are constituted by charging/discharging circuits having relatively large time constants, for example, and have a level corresponding to the average value of each of the signals of the transmitting system and the receiving system over a short period of time. configured to output a signal.

In the embodiment described above, the voice of the transmitter is input to the microphone 1, converted into an electrical signal, amplified by the amplifier 3, and taken into the comparator circuit 9 as a signal of the transmitter system 2. Then, the signal further amplified by the amplifier is given a loss amount in the variable loss circuit 4, which reduces the amount of loss when the device is in the transmitting state, and provides a loss amount that does not cause the device to make a sound when it is in the receiving state. Furthermore, after being amplified by the gain of the gain expansion circuit 17 determined by the gain control circuit 19, the signal is outputted to the communication line 13 as a transmission signal via the side sound circuit 12.

The received signal is input to the communication line 13, passes through the side sound protection circuit 12, and then is passed through the gain compression circuit 1 determined by the gain control circuit 19.
After being amplified with a gain of 8, in the variable loss circuit 8, a loss amount opposite to that of the variable loss circuit 4 is controlled and given by the output of the comparator 7 page 10 supplied via the inverter 11, and the receiving system 6 The signal is taken into the comparator circuit 9, amplified by the amplifier 7, and supplied to the speaker 5, where it is output as the voice of the receiver.

Here, the comparator circuit 9 and the comparator 10 determine whether the device is transmitting or receiving and output the result.The comparator circuit 9 uses the output of the transmitting system 2 and the output of the receiving system 6 as envelope inputs, and outputs " Transmission system 2/
The receiving system 6 outputs the ratio value and compares it with the set value T in the comparator 10. If the output of the comparator circuit 9 is larger, it is determined to be the transmitting state, and if it is smaller, it is determined to be the receiving state. judge. Based on the output of the comparator 10, a detection circuit controls the loss amount of the variable loss circuit 4.8 so as not to generate noise, controls the switching circuit 18, and detects the fixed time average value in the gain control circuit 15. 14. Select which output of 15 to input. Therefore, according to the above embodiment, in the transmitting state, even if the external noise is the same, the transmitting signal becomes smaller and the input from the transmitting system 2 (output of the detection circuit 14) is input to the gain control circuit 19. As shown in FIG. 3, when the S/N between the sidetone of the transmitted signal and the received signal becomes 1 QdB smaller than the reference input St, the S/N of the conventional S/N is QdB.
In the Joetsu example, S (received signal) - 1, odn ÷ 2 = -5 dBN (side tone signal) - 10 dB x 2 ÷ 2 = -10 dB, and the amount of side tone attenuation does not change, but only the S/N is different from the conventional one. It's from p5
dB, and the reception interrupt performance is significantly improved.

In the receiving state, the input to the gain control circuit 19 (output of the detection circuit 15) is 10 d compared to the reference human power St.
When B is small, the compression ratio in the gain compression circuit 18 is 1/1.
Since it is 0°'5, it is compressed by 5 dB. Similarly, when the input is 20 dB smaller, it has the AGO effect of compressing J and Q dB. At this time, since the gain expansion circuit on the transmitting side also expands at an expansion rate of 1005 reciprocally, the loop gain within the device remains constant regardless of the input level of the gain control circuit 19. As a result, the variable loss amount by the voice switch control can be easily set to the knowing limit value of the device, and the nine-page state can be achieved, which is almost the same as the simultaneous call state, and the call quality is significantly improved.

Effects of the Invention As is clear from the embodiments described above, the present invention provides variable loss circuits in the transmitting system and the receiving system, compares the signals of the transmitting system and the receiving system, and uses the results to compare the signals of the transmitting system and the receiving system. The system is constructed so that the loss of the variable loss circuit of each of the receiving system is reduced when receiving a call, and a detection circuit is separately provided to detect the constant time average value of each signal of the sending system and the receiving system. It is constructed so that the gain of the gain expansion circuit and gain compression circuit provided in the transmitting system and the receiving system are controlled reciprocally by the output of the circuit, so that the transmitting signal becomes smaller even when the external noise is the same. As a result, even if the ratio of external noise increases, if the output of the detection circuit 14 decreases, the S/N ratio of sidetone to the other party's signal from the communication path will be significantly improved, and accordingly, accurate reception interruption will be possible. It has the advantage that performance can be obtained.

[Brief explanation of drawings]

FIG. 1 is a 10-page diagram of a conventional hands-free communication device, FIG. 2 is a block diagram of an embodiment of the hands-free communication device of the present invention, and FIG. 3 is a gain compression circuit used in the same embodiment. FIG. 3 is an input/output characteristic diagram of a gain expansion/contraction circuit. ■...Microphone, 2...Talking system, 3.7...
Amplifier, 4.8... Variable loss circuit, 5... Speaker, 6... Receiving system, 9... Comparison circuit, 10... Comparator, 11... Inverter, 12... Soundproofing sidetone circuit,
13... Communication path, 14.15... Detection circuit, 16.
...Switching circuit, 17...Gain expansion circuit, 18
...gain compression circuit, 19...gain control circuit.

Claims (1)

[Claims] A variable loss circuit is installed in the transmitting system and the receiving system.
The output of the comparison means that compares the signals of the receiving system is used to control the variable loss of the transmitting system when transmitting and the receiving system when receiving a call. A hands-free system that is equipped with a detection circuit that detects the value, and uses the output of these detection circuits to switch and reciprocally control the gains of the gain expansion circuit and gain compression circuit provided in the transmitting system and the receiving system, respectively. Telephone device.