JPH01179525A - Bidirectional amplifier - Google Patents

Abstract

PURPOSE:To improve the quality of a call by adjusting the gain of a gain adjusting amplifier and the attenuation of a voice attenuator by an adjusting means provided on a line current detection circuit in response to the current of a subscriber line detected respectively by the line current detection circuit. CONSTITUTION:The current of subscriber lines 7, 8 is detected by line current detection circuits 12, 13, the adjusting means in response to the amplitude of the current to be detected adjusts the gain of gain adjusting amplifiers 5, 5', 6, 6' and the voice level detection comparator regulates the attenuation of voice of voice attenuators 10, 11 inserted in the inferior side path. Thus, the switching time from the state that the voice is attenuated in the inferior state till the state that the voice is inputted, the superior state is attained and the insertion loss due to the attenuator is lost is shortened. Thus, the interruption of the heat of the call is avoided and the quality of the call is improved.

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to a bidirectional amplifier that compensates for call loss in a subscriber line.

<Prior Art> Conventionally, such a bidirectional amplifier is shown in FIG. 2. This bidirectional amplifier connects subscriber line 2! The two-wire/four-wire conversion circuit 22 converts the audio signal sent from the first
The audio signal is transmitted to the communication path 23, and the amplifier 25 amplifies it and sends it out to the subscriber line 27 via the two-wire/four-wire conversion circuit 26, while the audio signal sent from the subscriber line 27 is The two-wire/four-wire conversion circuit 26 transmits the signal to the second communication path 28, the amplifier 29 amplifies the signal, and sends it to the subscriber line 21 via the two-wire/four-wire conversion circuit 22. In this way, losses in subscriber lines 2I and 27 are compensated for by amplifiers 25 and 29, respectively.

In this case, the balanced circuit networks 31 and 32 connected to the two-wire and four-wire conversion circuit 22 and the two-wire and four-wire conversion circuit 26, respectively.
If the impedances of the subscriber lines 21 and 27 perfectly match the impedances of the subscriber lines 21 and 27, the sound output from the amplifier 25 will not be transmitted to the amplifier 29 through the two-wire/four-wire conversion circuit 26, Further, the audio output from the amplifier 29 is not transmitted to the amplifier 25. However, in reality, the impedances of the subscriber lines 21 and 27 are not constant due to differences in distance from the exchange, and therefore impedance matching with the balanced circuit networks 31 and 32 is not completely achieved. As a result, the audio output from the amplifier 25 is transferred to the two-wire/four-wire conversion circuit 26.
The signal is then input to the amplifier 29 as an echo. Also,
The audio output from the amplifier 29 is transferred to the two-wire and four-wire conversion circuit 2.
2 and is input to the amplifier 25 as an echo. At this time, when the sum of the gains of the amplifiers 25 and 29 exceeds the sum of the echo attenuations of the two-wire and four-wire conversion circuits 22 and 26, this bidirectional amplifier enters an oscillation state.

In order to prevent this oscillation state, as shown in Figure 3,
The audio levels of the first communication path 23 and the second communication path 28 are compared by the audio level detection comparator 33, and audio attenuators 35 and 36 are inserted into the communication path with the lower audio level to reduce the echo. That's what I do. If the audio level on the channel in which the audio attenuator is inserted becomes higher than the audio level on the other channel, the audio attenuator is disconnected and the audio is transferred to the channel with the lower audio level. The insertion of the audio attenuator is switched by inserting the attenuator. Note that in order to insert the audio attenuators 35 and 36, the audio on the first communication path 23 is amplified by the amplifiers 25a and 25b, and the audio on the second communication path 28 is amplified by the amplifier 52.
9a and 29b are used for amplification.

<Problem to be Solved by the Invention> However, in the conventional bidirectional amplifier, the insertion of the audio attenuator is switched from a state in which the audio level is attenuated by the maximum attenuation m determined by the audio attenuator. As a result, there were problems in that the switching time was long, the beginning of the conversation was cut off, and the quality of the conversation deteriorated.

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a bidirectional amplifier that has a short attenuator switching time, has no cutoff at the beginning of words, and has good speech quality.

<Means for Solving the Problems> In order to achieve the above object, the bidirectional amplifier 2g of the present invention transmits the audio signal from the first subscriber line to the first communication path, while transmitting the audio signal from the second communication path. a first two-wire/four-wire converter circuit for transmitting a voice signal to the first subscriber line; a second transmitting signal to said second subscriber line;
a two-wire/four-wire conversion circuit; a first amplifier with adjustable gain for amplifying the audio signal on the first communication path; a second adjustable gain amplifier that amplifies the audio signal on the second communication path; A sound attenuator provided in each of the first and second communication paths compares the audio level of the first communication path and the second communication path, and determines the sound level of the communication path with the lower audio level. an audio level detection comparator that operates an attenuator; a first line current detection circuit that detects the line current of the first subscriber line; and a second line current that detects the line current of the second subscriber line. The detection circuit adjusts the gain of the first amplifier and the second amplifier according to the magnitude of the current detected by the first line current detection circuit and the second line current detection circuit, and the audio level detection comparator. The sound attenuator is operated by the sound attenuator.

(Function) First, the first amplifier amplifies the audio signal from the first subscriber line transmitted to the first communication path by the two-wire/four-wire conversion circuit, and the second two-wire/four-wire conversion circuit amplifies the audio signal from the first subscriber line. A second amplifier amplifies the voice signal from the second subscriber line transmitted to the second subscriber line.Also, a voice level detection comparator compares the voice level of the first communication path and the voice level of the second communication path. Operate the voice attenuator installed on the communication path with the lower level.Meanwhile,
Adjustment means according to the magnitude of the current detected by the first line current detection circuit that detects the line current of the first subscriber line and the second line current detection circuit that detects the line current of the second subscriber line. adjusts the gain of the first amplifier and the second amplifier.
At the same time, the amount of attenuation of the audio attenuator operated by the audio level detection comparator is adjusted. Therefore, the switching time of the attenuator is shortened, the beginning of words is not cut off, and the quality of speech is improved.

<Example> Hereinafter, the present invention will be explained in detail with reference to illustrated embodiments.

In FIG. 1, reference numeral 1 transmits the voice signal sent from the subscriber line 7 to the first communication path 15;
A two-wire/four-wire converter circuit 5 sends the human-powered voice signal to the subscriber line 7; 1. The voice signal input from the communication path 15 is transmitted to the subscriber line 8.
The two-wire/four-wire conversion circuits 3.4 are connected to the two-wire/four-wire conversion circuits 1.2, respectively, and are balanced circuit networks for impedance matching with the subscriber line 7.8.

The audio signal transmitted from the two-wire/four-wire conversion circuit 1 to the first communication path 15 is amplified by the gain control amplifiers 5, 5° and sent to the subscriber line 8 via the two-wire/four-wire conversion circuit 2. Also, the gain control amplifier 6.6'' amplifies the audio signal transmitted from the two-wire/four-wire conversion circuit 2 to the second communication line 16, and sends it to the subscriber line 7 via the two-wire/four-wire conversion circuit 1. do. The losses caused by the subscriber lines 7 and 8 are compensated for by the gain adjustment amplifiers 5.5° and 6.6°, respectively.

Further, the voice level detection comparator 9 compares the voice level of the first communication path 15 and the voice level of the second communication path 16, and the voice level of the first communication path 15 is higher than the voice level of the second communication path 16. If it is large, the voice attenuator 1 is installed in the second communication path 16.
1, and vice versa, the voice attenuator 10 is inserted into the first communication path 15. The audio attenuator 10.2 attenuates echoes leaking from the two-wire/four-wire conversion circuit 1.2 and prevents this bidirectional amplifier from going into oscillation.

The gains of the gain adjustment amplifiers 5, 5°, and 6.6° and the attenuation of the audio attenuator 10.11 are determined by the line current detection circuit 12.
The adjustment means provided in 13 controls this line current detection circuit 12.
13 respectively adjust according to the detected current in the subscriber line 7.8.

That is, when the line length of the subscriber line 7.8 is long, the loop current in the line becomes small because the communication loss in the subscriber line 7.8 is large. In such a case, the gain adjustment amplifier 5.
The gains at 5°, 6, and 6° are increased to compensate for the loss in subscriber line 7.8.

And audio level detection comparison at the same time? S and 9 are controlled to increase the amount of attenuation of the audio attenuator 10 or 11 that enters the inferior communication path where the audio level is low, resulting in a two-wire and four-wire conversion circuit! , 2. The total gain of the loop 14 consisting of the amplifiers 5.5°, 6.6° and the audio attenuator 10.11 is set to be less than 0 dB-α dB (α: housing margin).

On the other hand, when the line length of the subscriber line 7.8 is short, the loop current in the line becomes large because the communication loss in the subscriber line 7.8 is small. In such a case, the gain adjustment amplifier 5.5°,
At the same time as lowering the gain of 6.6', the attenuation amount of the voice attenuator IO or 11 entering the inferior communication path is lowered. Even if the attenuation is lowered in this way, the gain adjustment amplifier will still work at 5.5° and 6.6°.
Since the gain of the loop 14 is low, the total gain of the loop 14 is low and oscillation is prevented.

In this way, the line current detection circuits 12.13 detect the currents in the subscriber lines 7.8, and the adjustment means adjusts the gain adjustment amplifiers 5, 5°, 6, 6 depending on the magnitude of the detected currents.
Since the sound level detection comparator adjusts the gain of ° and the attenuation m of the sound attenuators 10 and 11 inserted into the path on the inferior side, from the state where the sound is attenuated in the inferior state,
The switching time until the voice enters the dominant state and the insertion loss due to the attenuator is eliminated is shortened, so that the beginning of the speech is not cut off, and the quality of the speech is improved.

In the above embodiment, the gain adjustment amplifier is 5.5°.

Although the circuit current detection circuits 12 and 13 are provided with adjustment means for adjusting the gain of 6.6° and the attenuation m of the audio attenuators 10 and 11, they may also be provided in the audio level detection comparator 9.

<Effects of the Invention> As is clear from the above, the bidirectional amplifier of the present invention has the following effects:
The gain of the first amplifier that amplifies the audio signal from the first subscriber line that the two-wire four-wire conversion circuit transmits to the first communication path, and the gain of the first amplifier that amplifies the audio signal from the first subscriber line that the two-wire four-wire conversion circuit transmits to the second communication path. A gain and voice level detection comparator of a second amplifier for amplifying the voice signal from the second subscriber line, which operates by comparing the voice level of the first communication path and the voice level of the second communication path, operates the voice signal. A first current detection circuit that detects the line current of the first subscriber line and a line 1u current of the first subscriber line detect the amount of attenuation of the voice attenuator installed in the communication path with the lower level. Since the adjustment means adjusts according to the current detected by the second current detection circuit, the switching time from the low audio level to the high audio level and the loss of insertion loss caused by the attenuator is shortened. , Therefore, the beginning of the word is not cut off, and the quality of the call is improved.

[BRIEF DESCRIPTION OF THE DRAWINGS] FIG. 1 shows a circuit t1 of an embodiment of the bidirectional amplifier of the present invention.
FIG. 2 is a block diagram showing the circuit configuration of a conventional bidirectional amplifier, and FIG. 3 is a block diagram showing the circuit configuration of a conventional bidirectional amplifier using the voice switching method. ! , 2... Two-wire four-wire conversion circuit, 3.4... Balanced circuit network, 5.5°, 6.6'... Gain adjustment amplifier, 7.8
...Subscriber line, 9...Audio level detection comparator, to
, tt...Audio attenuator, 12.13...Line current detection circuit, I5...First communication path, I6...Second communication path.

Claims (1)

[Claims] (1) a first two-wire/four-wire conversion circuit that transmits an audio signal from a first subscriber line to a first communication path, and transmits an audio signal from a second communication path to the first subscriber line; a second two-wire/four-wire conversion circuit that transmits a voice signal from a second subscriber line to the second communication path and transmits a voice signal from the first communication path to the second subscriber line; a first gain-adjustable amplifier that amplifies the audio signal on the first communication path; a second gain-adjustable amplifier that amplifies the audio signal on the second communication path; A voice level detection comparison that compares the voice level of the first communication path and the voice level of the second communication path with the voice attenuators provided for each, and operates the voice attenuator of the communication path with the lower audio level. a first line current detection circuit that detects the line current of the first subscriber line; a second line current detection circuit that detects the line current of the second subscriber line; and the first line current detection circuit. and the magnitude of the current detected by the second line current detection circuit, the gain of the first amplifier and the second amplifier is adjusted, and the amount of attenuation of the audio attenuator operated by the audio level detection comparator is adjusted. A bidirectional amplifier characterized in that it is equipped with an adjusting means for