JPH0514490A - Pushbutton telephone set - Google Patents

Abstract

PURPOSE:To make the extension talking quality equal to the talking quality of an external line. CONSTITUTION:When an external line selection button 9 is depressed at talking with an external line, a low level is outputted to an output terminal of a state control circuit 8, an extension external line automatic changeover switch 7 is turned off, no current is supplied from a DC power supply circuit 4 to a speech circuit 5 and the current is supplied from a station side via line terminals 1, 2 and a rectifier circuit 3. When an extension selection button 10 is depressed at the extension talking, the output terminal of the state control circuit 8 goes to a high level and the extension external line automatic changeover switch 7 is turned on, power is supplied from a DC power supply circuit 4 to the speech circuit 5 and the extension talking with plural other pushbutton telephone sets connecting to the same pushbutton telephone master set in multi-drop system is attained. In this case, an extension state output circuit 12 detects a high level of the output of the state control circuit 8 to activate an automatic changeover switch 11. The automatic changeover switch 11 activates a 3dB pad terminal of the speech circuit 5 to set the speech circuit 5 into the extension speech state.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a key telephone, and more particularly to a key telephone connected to an analog small capacity key telephone main unit by a multi-drop method.

[0002]

2. Description of the Related Art Conventionally, this kind of button telephone is constructed so as to control an extension / outside line automatic changeover switch by a control signal from a state control circuit corresponding to a pressed extension or outside line selection button, and a call circuit The same circuit was used for both internal and external calls.

Next, a conventional button telephone will be described with reference to the drawings.

FIG. 2 is a block diagram showing an example of a conventional button telephone.

In FIG. 2, the conventional button telephone has a line terminal 1 and a line terminal 2 connected to a line to a key telephone main unit (not shown) and a rectifying circuit for rectifying a current from the key telephone main unit. 3, a DC power supply circuit 4 for supplying a direct current to the button telephone of the conventional example, an outside line selection button 9 for selecting an outside line, an extension selection button 10 for selecting an extension line, an outside line selection button 9 or an extension selection button. 1
State control circuit 8 that outputs a state signal when 0 is pressed
And a call circuit 5a from the DC power supply circuit 4 according to the status signal from the status control circuit 8
It is configured to have an extension / outside line automatic changeover switch 7 for switching the supply of a DC current to the DC line, and a constant current circuit 6 for converting the DC current from the DC power supply circuit 4 into a constant current and supplying it to the communication circuit 5a. .

Next, the operation of this conventional example will be described.

When the outside line selection button 9 is pressed during a call with an outside line, the output terminal of the state control circuit 8 outputs a low level, the extension / outside line automatic changeover switch 7 is turned off, and the DC power supply circuit No current is supplied from 4 to the call circuit 5a, but current is supplied from the station side through the line terminals 1 and 2 and the rectifier circuit 3.

When the extension selection button 10 is pressed during an extension call, the output terminal of the state control circuit 8 becomes a high level, the extension / outside line automatic switch 7 is turned on, and the DC power supply circuit 4 switches the call circuit. An electric current is supplied to 5a, and an extension call can be made with other key telephones that are connected in plurality. At this time, the supply from the central line is cut off on the side of the key telephone main unit.

[0009]

The above-mentioned conventional button telephone uses the same circuit for the call circuit during the extension call and the outside call, and the distance between the line and the button to be connected during the outside call and the button to be connected. Considering the factors that the number of telephones is small and the current supplied during extension calls is small but the call path is familiar, the impedance fluctuation seen from the call circuit is large, the side tone balance is disturbed, and the optimum call quality for all. There is a problem that it is extremely difficult to secure. For this reason, most circuit configurations of conventional button telephones prioritize the quality of outside line calls,
It has a drawback that the quality of extension calls cannot be secured sufficiently.

[0010]

A button telephone according to the present invention is an external line selection button for connecting an analog small-capacity button telephone main unit by a multi-drop method and selecting an external line.
An extension selection button for selecting an extension, a state control circuit that sends a state signal by pressing the outside selection button or the extension selection button, and an extension selection indicating that the extension selection button from this state control circuit is pressed In a key telephone having a current selector switch for supplying a direct current from a direct current supply circuit to a communication circuit only when a status signal is received, the communication circuit has a predetermined connection terminal to a gain attenuator, and An extension state detection circuit that detects that the extension selection state signal is output from the state control circuit, and a changeover switch that connects the communication circuit to a connection terminal to the gain attenuator by a control signal from the extension state detection circuit. have.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, the present invention will be described with reference to the drawings.

FIG. 1 is a block diagram showing an embodiment of the present invention.

In FIG. 1, the key telephone of the present embodiment is given the same number as the same configuration requirement as that of the conventional button telephone shown in FIG. 2, except that the telephone circuit 5a in the conventional example has 3 dB. Call circuit 5 with pad terminals
An extension state detection circuit 12 for detecting that the output of the state control circuit 8 is at a high level and the extension has been selected; and a control signal from the extension state detection circuit 12
Is connected to the 3 dB pad terminal to set the call circuit 5 to the extension call state.

Next, the operation of this embodiment will be described.

When the outside line selection button 9 is pressed during a call with an outside line, the output terminal of the state control circuit 8 outputs a low level, the extension / outside line automatic changeover switch 7 is turned off, and the DC power supply circuit 4 Current is not supplied from the station side to the call circuit 5, and the line terminals 1 and 2 from the station side
And a current is supplied via the rectifier circuit 3.

When the extension selection button 10 is pressed during an extension call, the output terminal of the state control circuit 8 becomes high level, the extension / outside line automatic changeover switch 7 is turned on, and the DC power supply circuit 4 to the call circuit 5 are turned on. The electric current is supplied to the key telephone main unit, and extension telephone communication with other key telephones connected to the same key telephone main unit in a multi-drop manner becomes possible. At this time, the supply from the station side is cut off on the key telephone main unit side.

At the same time, the extension state detection circuit 12 detects the output high level of the state control circuit 8 and operates the automatic changeover switch 11. The automatic changeover switch 11 turns on the 3 dB pad terminal of the communication circuit 5 to set the communication circuit 5 to the extension communication state.

[0018]

As described above, according to the present invention, an external line selection button for selecting an external line, an internal line selection button for selecting an external line, and an external line for connecting to an analog small-capacity button telephone main unit by a multi-drop method. A status control circuit that sends a status signal by pressing the select button or the extension selection button, and a call circuit from the DC supply circuit only when an extension selection status signal indicating that the extension selection button has been pressed is received from this status control circuit. In a key telephone having a current selector switch for supplying direct current to the telephone, the call circuit has a connection terminal to a predetermined gain attenuator, and an extension for detecting that an extension selection state signal is output from the state control circuit. Status detection circuit and changeover switch that connects the call circuit to the connection terminal to the gain attenuator by the control signal from the extension status detection circuit By having, since changeover switch when extension selection is connected the call circuitry to gain attenuator, there is an effect that it is possible to ensure the quality of extension call equal to the outside call quality.

[Brief description of drawings]

FIG. 1 is a block diagram showing an embodiment of the present invention.

FIG. 2 is a block diagram showing an example of a conventional key telephone.

[Explanation of symbols]

 1 line terminal 2 line terminal 3 rectifier circuit 4 DC power supply circuit 5, 5a speech circuit 6 constant current circuit 7 automatic extension / external line changeover switch 8 state control circuit 9 external line selection button 10 extension selection button 11 automatic changeover switch 12 extension state detection circuit

Claims (1)

Claims: 1. An external small capacity button telephone main unit is connected by a multi-drop method, an external line selection button for selecting an external line, an internal line selection button for selecting an internal line, and the external line selection button. Alternatively, a state control circuit that sends a state signal by pressing the extension selection button, and a call circuit from the DC supply circuit only when an extension selection state signal from the state control circuit indicating that the extension selection button is pressed is received. In a key telephone having a current selector switch for supplying a direct current to the call circuit, the communication circuit has a predetermined connection terminal to a gain attenuator, and the state control circuit outputs the extension selection state signal. And a connection terminal for connecting the communication circuit to the gain attenuator by a control signal from the extension state detection circuit. Key telephone characterized in that it comprises a selector switch for connecting.