JPH0771326B2 - Button telephone device - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a bus line type button telephone device having an extension call function.

2. Description of the Related Art Conventionally, as shown in FIG. 2, the bus line type button telephone device of this type has a station line run-in L1 and an extension line L2.
The main unit 3 having a power circuit 1, a CPU 2, etc., and the station line L1 and the extension communication line L2 are connected via bus lines B1 and B2, and an extension / station switching relay 4, a communication hybrid circuit 5, a main circuit It is composed of a plurality of telephones 9A, 9B, 9C having a CPU 6 for performing a data call with the device 3, a receiver unit 7 connected to the call hi-flid circuit 5, a microphone unit 8 and the like.

Then, during an extension call, the CPU2 of the main unit 3 is connected to the bus lines B1 and B
The state of the telephones 9A, 9B, 9C is managed via 2, and the extension / station line switching relay 4 is on the extension side, and the two telephones connected to the main device 3 and the extension call line L2 are used as a call loop. Is something that can be done.

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention However, in the above-mentioned conventional button telephone device, since the impedance of the extension call line L2 changes depending on the number of telephones 9A to 9C connected to the extension call line L2 of the main device 4, the call high bridge circuit 5 However, there is a problem in that good and stable side tone characteristics and howling characteristics cannot be obtained.

The present invention solves such conventional problems,
It is an object of the present invention to provide an excellent button telephone device capable of making an extension call with good and stable side tone characteristics and howling characteristics.

Means for Solving the Problems In order to achieve the above-mentioned object, the CPU of the main device recognizes the number of telephones connected to the extension communication line of the main device, and the impedance of the extension communication line of the telephone is The main unit is provided with an impedance adjusting unit that is constant regardless of the number of units.

Therefore, according to the present invention, the CPU of the main unit recognizes the number of telephones connected to the extension line of the main unit by the data communication between the main unit and the main unit by adjusting the impedance adjusting unit. The impedance of the extension communication line can be kept constant, regardless of the number of telephones connected to, and the operation of the call hybrid circuit can be performed satisfactorily and stably, and extension calls can be made with excellent sidetone characteristics and howling characteristics. Has the effect.

Practical Example FIG. 1 shows the configuration of an example of the present invention. In FIG. 2, 11 is a main unit, and 12A to 12C are telephones connected to the main unit.

The main device 11 has a power supply circuit 13 for the office line L1, the extension communication line L2, a CPU 14, an impedance adjusting unit 15 for the extension communication line L2, and the like. The impedance adjusting unit 15 connects the adjusting impedances 16a to 16c and the transistors 17a to 17c in series between the extension communication line L2 and the ground E, and the bases of the transistors 17a to 17c are connected via resistors 18a to 18c. Connected to the CPU 14.

On the other hand, each telephone 12A ~ 12C, the extension-station line switching relay 19,
Call hybrid circuit 20, CPU2 for data communication
1. It has a receiver unit 22 and a microphone unit 23 connected to the call hybrid circuit 20.

Next, the operation of the above embodiment will be described. In the above embodiment, during extension calls, the CPU 14 of the main device 11 causes the telephones 12A to 12
When the number of telephones 12A to 12C connected to the extension call line L2 is recognized by data communication with C, the transistors 17a to 17c of the impedance adjusting unit 15 are selected and conducted so that the insufficient impedance is included from the maximum number of connected telephones. Then, the impedance is adjusted to make the impedance of the extension line L2 constant. As a result, the operation of the call hybrid circuit 20 can be made stable and favorable, and extension calls can be made with excellent sidetone characteristics and howling characteristics.

EFFECTS OF THE INVENTION As is apparent from the above-described embodiment, the present invention adjusts the impedance adjustment unit of the extension call line by the CPU of the main device that recognizes the number of telephones connected to the extension call line, regardless of the number of telephones. Since the impedance of the extension call line is constant, the call hybrid circuit can be operated satisfactorily and stably, and the extension call can be performed with excellent sidetone characteristics and howling characteristics.

[Brief description of drawings]

FIG. 1 is a schematic block diagram of a button telephone device according to an embodiment of the present invention, and FIG. 2 is a schematic block diagram of a conventional button telephone device. 11 ... Main unit, 12A-12C ... Telephone, 13 ... Extension call line power supply circuit, 14 ... CPU, 15 ... Impedance adjustment section, 19 ... Extension 1-station line switching relay, 20 ... Call hybrid Circuit, 21 …… CPU, L1 …… station line, L2 …… extension call line, B1, B2 …… bus line.

Claims (1)

[Claims] Claim: What is claimed is: 1. The impedance of an extension line when the CPU recognizes the power supply circuits for the office line and the extension line, the CPU for data communication, and the number of telephones connected to the extension line. And a main unit having an impedance adjusting unit for adjusting so as to keep constant.