JPS61256854A - Key telephone system - Google Patents

Abstract

PURPOSE:To obtain the optimum volume of a call by providing a means which automatically adjust the level of a call signal at the optimum level based upon the variation of the DC current of a connected telephone line. CONSTITUTION:A DC current detection circuit 28, two-wires/four-wires conversion circuits 221 and 241, variable gain amplifier circuits 222 and 223, and also a control circuit 23 for the above circuits are provided. When a key telephone system is connected with a main wire 20, the DC current detection circuit 28 reads that and sends the detecting output to a control circuit part 23. The control circuit 23 discriminated the detecting output and makes the gain of either or both of the variable gain amplifiers 222 and 223 within a main wire interface part 22 change. Thereby, either or both of a transmitting sound volume and a receiving sound volume is/are increased or decreased and the sound volume is set at the optimum level.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a button telephone device. Here, the term "key telephone device" refers to a means for accommodating one or more telephone lines (including a private branch exchange line), a plurality of button telephones, and a means by which the telephones communicate with each other, and a means for communicating between the telephone and the above telephone line. A device equipped with a means for connecting a telephone line and a means for changing the telephone to be connected while keeping the telephone line on hold.

〔overview〕

The present invention provides a button telephone device that detects the magnitude of the direct current in the telephone line and adjusts the magnitude of the call signal, thereby automatically setting the call volume to the optimum level regardless of the transmission loss of the telephone line. It is possible to set the following.

[Conventional technology]

Conventionally, in this type of button telephone device, as shown in FIG. 2, calls between the button telephone 17 and the telephone line 10 are carried out through a telephone interface section 14, a call path switch section 15, and a central office line interface section within the main device 11. It was carried out through 12.

Further, the office line interface section 12, the telephone interface section 14, and the communication path switch section 15 are controlled by the control circuit section 13. In the figure, 16 is a call signal.

[Problem that the invention seeks to solve]

In the above-mentioned conventional button telephone device, the telephone line and the button telephone are connected as two wires, so the call signal cannot be amplified within the main device, and the gain or loss during a call is limited to the transmission. Both voice and voice reception remained constant regardless of the line conditions of the telephone line. On the other hand, telephone lines generally have high loss when the direct current is low, and low loss when the direct current is large. Therefore, when connected to a high-loss telephone line, the volume of sending and receiving calls decreases, causing a problem in making calls.

SUMMARY OF THE INVENTION An object of the present invention is to provide a button telephone device that automatically sets the call volume to an optimal level regardless of the magnitude of loss in the connected telephone line by eliminating the above-mentioned drawbacks.

[Means for solving problems]

The button telephone device of the present invention includes means for converting a speech signal of a connected telephone line into two-wire and four-wire, and means for adjusting the level of the converted speech signal by the magnitude of the direct current of the telephone line. have.

[Effect]

The present invention makes it possible to detect the loss of a telephone line in which a plurality of button telephones are connected and have different losses by the magnitude of the direct current of the line, thereby detecting the magnitude of the two-wire, four-wire converted call signal. For example, by changing the gain of the amplifier, the call volume can be automatically set to the optimal level.

〔Example〕

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

FIG. 1 is a block diagram of an embodiment of the present invention. The main device 21 according to this embodiment includes a DC current detection circuit 28
, central office line interface section 22, communication path switch section 25,
Consists of a telephone interface section 24 and a control circuit section 23, through which a button telephone 27 and a telephone line 20 are connected.
is connected.

In the station line interface section 22, a station '4R29 connected to the DC current detection circuit 28 is connected to the two-wire side of the two-wire/four-wire conversion circuit 221, and a station '4R29 connected to the DC current detection circuit 28 is connected to one of the four-wire sides. A variable gain amplifier 22 that amplifies the output of
2 are connected in series, and the output signal from the two-wire/four-wire conversion circuit 221 is amplified to the other four-wire side, and the communication path switch section 2
A variable gain amplifier 223 for sending out to 5 is connected in series.

Further, in the telephone interface section 140, there is a two-wire/four-wire conversion circuit 241 connected to the call path switch section 25 on the four-wire side, and the two-wire side is connected to the button telephone 27. In the figure, 26 and 29 are call signals.

The features of the present invention include a DC current detection circuit 28, a two-wire and four-wire conversion circuit 221.241, and a variable gain amplifier circuit 222.2.
23 and a control circuit 23 for them.

Next, the operation of this embodiment will be explained.

When the button telephone device of this embodiment is connected to the central office line 20, the DC current detection circuit 28 reads the DC current and sends the detection output to the control circuit section 23. The control circuit section 23 judges the detection output and varies the gain of one or both of the variable gain amplifiers 222 and 223 in the station line interface section 22. As a result, one or both of the transmitting volume and the receiving volume is increased or decreased, and the volume is set to the optimum level.

In the above-described embodiment, a variable gain amplifier is used as a means for varying the sound volume, but other means such as a variable resistance attenuator may be used with the gain of the amplifier being constant.

〔Effect of the invention〕

As explained above, the present invention provides a means for automatically adjusting the level of a call signal to an optimum level based on changes in the direct current of the connected telephone line, thereby making it possible to connect to a high-loss telephone line. This feature has the effect of automatically preventing the call volume from decreasing even in such cases, and ensuring that the optimal call volume is always obtained.

In particular, the present invention has the advantage that it can be directly applied to key telephone equipment equipped with a time-division call path switch that requires two-line and four-wire conversion.

At the same time, during the installation work of the key telephone device, the optimum call volume can be automatically set, which has the effect of reducing the number of work hours.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing an embodiment of the present invention. FIG. 2 is a block diagram showing a conventional example. 10.20...Station line, 11.21...Main device, 12
．． 22... Office line interface section, 13.23...
Control circuit section, 14.24... Telephone interface section, 15.25... Call path switch section, 16.26.2
9... Call signal, 17.27... Button telephone, 2
8... DC current detection circuit, 221.241... Two-wire four-wire conversion circuit, 222.223... Variable gain amplifier. Patent applicant NEC Corporation 2-1-1 agent Patent attorney Nao Takashi Ide Figure 32 of the conventional example overall diagram

Claims (1)

[Claims] (1) A button telephone device comprising means for converting a call signal of a connected telephone line into two-wire and four-wire, and means for adjusting the level of the converted call signal according to the magnitude of the direct current of the telephone line. .