JPS60257648A - Branching and coupling circuit - Google Patents

Abstract

PURPOSE:To transmit almost uniformly a voice independently of loss of a transmission system by allowing each of AGC circuits to control the gain of a variable gain branching amplifier and a variable gain coupling amplifier for telephone lines based on the difference between a voice level and a reference level. CONSTITUTION:Variable gain branching amplifiers 301-30n whose gain is controlled by an external control signal and the AGC circuits 401-40n detecting the transmission level, comparing it with a prescribed level and controlling the gain of the amplifiers 301-30n by means of comparison information are connected to transmission lines T1-Tn of each subscriber. Each of the circuits 401-40n controls the gain of the variable gain branching amplifier and the variable gain coupling amplifier for telephone line to which the input terminal of the said circuits is connected based on the difference between the voice level and the scheduled level of the transmission line.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to a branching/coupling circuit that branches and couples a plurality of (5 or more) 4-wire signal paths to enable mutual communication. The present invention provides a branching/coupling circuit useful in configuring a conference telephone system using telephone lines.

[Conventional technology]

Telephone lines are generally 4 lines for the city evening exchange system.

The subscriber system consists of two or four lines. If the subscriber system is 2-wire, a 2-wire/4-wire conversion circuit is installed in the terminal exchange system and connected to the toll system. In order for six or more subscribers to communicate with each other using such telephone lines, a branching/combining circuit for each line is required. This branch/connection circuit is generally connected to a four-wire section.

Conventionally, such branching/coupling circuits have been used.

A multi-stage connection method of branch amplifier circuits used in the configuration of a meeting line, or a method in which a plurality of branch amplifiers and a plurality of coupling amplifiers are coupled in a matrix network is known. When it is necessary to branch and couple a large number of subscribers, the latter matrix network, which is located at a point on the facility and can branch and couple radially, is usually installed in a telephone exchange or on the side of a private exchange.

[Problem that the invention seeks to solve]

In this case, each subscriber can be branched and connected to each other using the above-mentioned branching/coupling circuit to form a conference telephone system, but the loss in the transmission system from each subscriber to this branching/coupling circuit is not uniform. . In this case, it is expected that the voices of each subscriber may be loud for some subscribers, while others may be soft and difficult to hear.

The object of the invention is in conference telephone systems and the like.

Each subscriber's audio to other subscribers except yourself.

The object of the present invention is to provide a branching/coupling circuit that enables almost uniform transmission regardless of variations in loss in a transmission system.

[Means for solving problems]

According to the present invention, each of the variable gain branching amplifiers has at least six AGC circuits whose input ends are connected to a branching/combining circuit connected between at least six telephone lines.

The output end is connected to the input end of all the variable gain coupling amplifiers for the remaining telephone lines except for the telephone port m to which the input end is connected, and each of the AGC circuits listed in IIJ has the following:
The gain of the variable gain branching amplifier and the 5J variable gain combining amplifier for the telephone line to which the input end is connected is controlled by the difference between the voice level of the transmission path of the telephone line and a predetermined level. A characteristic branching/coupling circuit can be obtained.

〔Example〕

Next, embodiments of the present invention will be explained with reference to the drawings.

FIG. 1 shows an embodiment of the invention. 4-wire subscriber telephone terminals 101 to 10. The signals from the network are mutually branched and combined in the broadcasting/combining circuit 20, and the voice of each subscriber is transmitted to all other subscribers except the subscriber. In Figure 1,
The transmission lines T1 to Tn of each subscriber's line are provided with variable first gain branching amplifiers 301 to 50n whose output is controlled by an external control signal, and which detect the transmission level and set it to a predetermined level. AGC (automatic first control) circuits 401 to 40n are connected to compare and control the gain of the variable gain coupling amplifier 3Q-3C1 based on the comparison information. The receiving lines R1 to R of each person have a gain rl'l for the external control signal.
Variable gain coupling amplifiers 501 to 50° that can be connected to the signal line 11m are connected. Each of the variable gain branching amplifiers 50, ~30n is connected to all the variable gain combining amplifiers 501~5 for the remaining telephone lines except for the telephone line to which its input end is connected.
The output end is connected to the input end of 0n. In this relationship, the variable gain branching amplifiers 301 to 3On and the variable gain coupling amplifiers 50° to 50 are connected in a matrix. The variable gain coupling amplifiers 501 to 50n are also AG
The gain is controlled by the output signals of the C circuits 401-40. In this way, the AGC circuit 40. ~40n is the gain of the variable gain branching amplifier and variable gain combining amplifier for the telephone line to which its input end is connected.

Predetermine the audio level of the sending path of the telephone line.
"1. Controlled by the difference from the level. The predetermined level in the AGC circuits 401 to 40n is
All have the same value.

In this branching/coupling circuit 20, when there is an audio signal from a certain subscriber, at the transmitter's power point of the two branching/coupling circuit 2D,
Depending on the level of the voice level, the gain of the variable gain branching amplifier of the subscriber's line is controlled, thereby adjusting the output level to an appropriate level. Gain is properly controlled. That is, the first gains of the variable gain branching amplifier and the variable gain coupling amplifier can be set so as to substantially compensate for the loss from the subscriber to the branching/coupling circuit 20. This operation is possible only after each subscriber speaks.9For example, at the beginning of a conference call, the moderator may ask each subscriber to briefly introduce themselves (for about a few seconds), and then each variable gain amplifier It would be possible to set the gain to an appropriate value.

According to this embodiment, for example, it is possible to make the audio level of each subscriber almost the same value at the branch output point in the branching/coupling circuit. Further, the voice level is distributed to other subscribers other than the subscriber at an appropriate gain commensurate with the loss of the transmission system for the subscriber. Therefore, the audio of any subscriber will be transmitted to all subscribers at approximately the same level, creating a desirable state for a conference.

FIG. 2 is an example in which the branching/coupling circuit 2o of FIG. 1 is applied to a two-wire telephone line. The 2-wire lines from the 2-wire subscriber terminals 601 to 60n are converted to 4-wire lines by 2-wire and 4-wire conversion circuits (hybrid circuits) 701 to 70n to prevent noise from occurring due to an increase in 4-wire loop gain. Reverberation control circuit 8
0. ~8on (these are realized with echo suppressors or echo cancellers) to the branching/coupling circuit 20. Said echo control circuit 80. - 9 branching/coupling circuits 2o are used due to the action of 8on. It is possible to avoid a noise state due to an increase in loop gain due to an increase in gain and signal superposition due to multiple loops. In this way, all subscribers can conduct conference calls on an equal footing.

Although FIGS. 1 and 2 show an example in which the branching/coupling circuit is applied to an analog line, the branching/coupling circuit of the present invention can be configured in the same way even if the two lines are digital. can. Furthermore, it is clear that even if each subscriber signal consists of a PCM multiplex signal, the two branching/combining circuits of the present invention can be constructed in the same way.

〔Effect of the invention〕

As described above, according to the present invention, it is possible to uniformly transmit each subscriber's voice to other subscribers except for the conference telephone system, regardless of variations in loss in the transmission system. This enables appropriate audio conferencing.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram showing a branching/coupling circuit according to an embodiment of the present invention, and FIG. 2 is a circuit diagram showing an application example of the branching/coupling circuit of FIG. 10.1[]2~10n...Subscription telephone terminal. 20 ・Branch/coupling circuit. 30.3012~3On...Variable gain branch amplifier. 401.402~40...AGC circuit. 50.502~50n...Variable gain coupling amplifier. 60.602~6On-2 wire type subscription terminal. 70, 702-7on...2-wire 4-wire conversion circuit. 80,, 802 to 80n... Reverberation control circuit.

Claims (1)

[Scope of Claims] 1. At least six AGC circuits connected between at least five telephone lines, each of the variable gain branching amplifiers having an input terminal connected to the telephone line. at the input end of all variable gain coupling amplifiers for the remaining telephone lines except . Each of the AGC circuits has an output terminal connected to it, and each of the AGC circuits adjusts the gain of the variable gain branching amplifier and the variable gain combining amplifier for the telephone line to which the input terminal is connected to the audio channel of the telephone line. A branching/coupling circuit characterized in that control is performed based on the difference between a level and a predetermined level.