JPH02124664A - Key telephone system - Google Patents

Abstract

PURPOSE:To balance both the speech states of trunk line talking and extension talking and to increase the transmission and reception sound volume when the impedance of speech lines differs from each other by devising the telephone set so that an exclusive balance network is selected depending on the speech state. CONSTITUTION:A changeover switch 10 connects a trunk line channel 1 and a 2/4-wire conversion circuit 3 of the channel and also a changeover switch 11 selects a trunk line speech balance network 6 in the speech circuit in the case of the speech of trunk line. On the other hand, the changeover switch 10 connects an extension channel 2 and the 2/4-wire conversion circuit 3 of the channel and also the changeover switch 11 selects an extension line speech balance network 7 in speech circuit in the case of the speech of the extension line. Thus, the sound volume of the transmission and reception is increased by taking the line balance in this way.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a key telephone device having a central office line calling function and an extension calling function.

BACKGROUND OF THE INVENTION FIG. 2 shows the structure of a conventional key telephone device. In FIG. 2, 1 is the office line communication path, 2 is the extension communication line, 3 is a 2-wire/4-wire conversion circuit, 4 and 5 are a receiving amplifier and a sending amplifier connected to the 2-wire/4-wire conversion circuit 3, and 6 8 is a receiver connected to the receiving amplifier 4, and 9 is a microphone connected to the transmitting amplifier 5. 2 wires A communication circuit consisting of a 4-wire conversion circuit 3, a receiving amplifier 4, a transmitting amplifier 5, a balance network 6 for central line communication, a receiver 8, and a microphone 9 is switched by a changeover switch 10, and is switched to central line communication path 1 during a central line communication. and is connected to extension line 2 during an extension call.

Therefore, in the above-mentioned conventional key telephone device, the balance network 6 for central line telephone calls is used for both the central telephone call and the extension telephone call.

In this manner, in the above-mentioned conventional key telephone device, the balance network 6 for central office line calls also serves as the balance network for extension calls.

Problems to be Solved by the Invention However, in the above-mentioned conventional button telephone device, the balanced network is one for central line calls. There was a problem in that if balance was taken during line calls, balance could not be achieved during extension calls.

The present invention solves these conventional problems, and provides a solution to both the central office line call and the extension call.
It is an object of the present invention to provide a button telephone device having a telephone communication circuit that can be balanced.

Means for Solving the Problems In order to achieve the above object, the present invention provides a balanced network for central office line calls, a balanced network for internal telephone calls, and a switchover to the balanced network for central office telephone calls at the time of a central office telephone call. It is equipped with a switching means for switching to the above-mentioned balance network for extension calls at times.

Effects The present invention has the following effects due to the above structure. In other words, the communication circuit has dedicated balanced networks for central office line calls and internal line calls, respectively.
Since switching is made to the dedicated balanced network according to the call status, even if the impedance of the call lines differs, it is possible to balance the call status of both the office line call and the extension call.

EXAMPLES Hereinafter, examples of the present invention will be described with reference to the drawings.

FIG. 1 shows the configuration of an embodiment of the present invention.

In this embodiment, the same parts as those in the conventional example described above are given the same reference numerals, and the explanation thereof will be omitted, and the different configuration will be explained. As shown in FIG. 1, the communication circuit is provided with a balance network 7 for extension calls in addition to the balance network 6 for office line calls, and these balance networks 6 and 7 for office line calls and extension calls are used during office line calls. and when making an extension call, they are switched by a changeover switch 11 and connected to the 2-wire/4-wire conversion circuit 3.

Next, the operation of the above embodiment will be explained.

At the time of a telephone call on the central office line, the changeover switch 10 connects the central office line communication path 1 and the 2-wire/4-wire conversion circuit 3 of the communication circuit to the connection 5. Switched to balance network 6. On the other hand, during an extension call, the changeover switch 10 connects the extension call path 2 to the 2-wire/4-wire conversion circuit 3 of the call circuit, and at the same time, the changeover switch 11 switches the call circuit to the balance network 7 for extension calls. .

In this way, according to the above embodiment, the dedicated balance network is switched depending on the call state, so even if the impedance of the call line is different, balance can be maintained in each call state. Furthermore, by achieving the balance as described above, it is possible to increase the size of the sending and receiving calls.

Effects of the Invention As described above, according to the present invention, in the communication circuit,
There are dedicated balanced networks for central office line calls and internal telephone calls, and the system switches to the above dedicated balanced network depending on the call status, so even if the impedances of the calling lines are different (6"-7), It is possible to balance both call status with extension calls, thereby increasing the volume of outgoing and incoming calls.

[Brief explanation of the drawing]

FIG. 1 is a schematic block diagram showing a key telephone device according to an embodiment of the present invention, and FIG. 2 is a schematic block diagram showing a conventional key telephone device. 1... Office line communication path, 2... Extension communication path, 3... 2
line 4-wire conversion circuit, 4... receiving amplifier, 5... transmitting amplifier, 6... balance network for central line communication, 7.
...Balanced network for extension calls, 8.Receiver, 9..Microphone, 10. 11... Selector switch.

Claims (1)

[Claims] A button telephone device comprising a balanced network for central office line calls, a balanced network for internal telephone calls, and a switching means for switching to the balanced network for central office line calls during a central office line call, and switching to the above balanced network for internal calls during an internal call. .