JPH0243886A - Pushbutton telephone set - Google Patents

Abstract

PURPOSE:To attain switching of a speech loop at a low current consumption by providing a photocoupler driving a semiconductor switch element inserted in a line and a control circuit isolated electrically to a trunk line and controlling the photocoupler. CONSTITUTION:When a current flows between output terminals of a control circuit 4, a light emitting element 61 of a photocoupler 6 is stimulated and a photodetector 62 arranged opposite thereto receives the light and a photoelectric conversion signal is outputted. The photodetector 62 forms a Darlington circuit in pairs with a transistor(TR) 63 and a current being a multiple of a CTR(current transfer ratio) of the light emitting element 61 is a collector current of the TR 63. Moreover, a current being a multiple of hFE (common emitter current amplification factor) of the collector current of the TR 63 flows to a semiconductor switch element 7. Thus, an output current of the control circuit 4 is I/(CTRXhFE), where I is a speech current flowing a channel thereby reducing the current consumption for switching of the speech loop considerably.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a button telephone device that controls the connection of a communication circuit to a central office line by a control circuit that is electrically insulated from the central office line.

2. Description of the Related Art As a conventional device of this type, the configuration shown in FIG. 2 is known.

In Fig. 2, 1 is a central office line, 2 is a polarity-potable diode bridge that is connected to the central office line 1 and keeps the polarity of the power applied to the oscillator (not shown) in the telephone equipment constant, and 3 is a diode bridge. 2 is a communication circuit connected to the output side of line 1; 4 is a control circuit electrically insulated from line 1; 5 is driven by control circuit 4, and its contact 5a is connected to diode bridge 2 and the communication circuit. This is a relay inserted in the communication path between 3 and 3.

In the configuration shown in FIG. 2, when the call loop is to be closed, the control circuit 4 excites the relay 5 and closes the contact 5a. This connects the diode bridge 2 and the communication circuit 3, and the communication circuit 3 functions.

Problems to be Solved by the Invention However, in the conventional configuration as described above, since the relay 5 is used to open and close the call loop, the current consumption is low, and the reliability is deteriorated due to the mechanical contact 5a. There is an issue of being inferior.

The present invention solves the conventional problems as described above.
It is an object of the present invention to provide a button telephone device that can open and close a call loop with low current and with high reliability.

Means for Solving the Problems In order to achieve the above object, the present invention provides a communication circuit connected to a central office line, and a semiconductor switch element inserted into a line connecting the communication circuit and the central office line. , a photocoupler that drives the semiconductor switch element, and a control circuit that is electrically insulated from the office line and controls the photocoupler.

action The present invention has the following effects due to the above configuration.

That is, the control output from the control circuit drives the light emitting element of the photocoupler and generates a photo-electrical conversion signal in the light receiving element disposed opposite to each other. The converted signal is amplified to turn on the semiconductor switch element and close the speech loop. Therefore, opening and closing can be performed without using a relay.

EXAMPLES Hereinafter, examples of the present invention will be described with reference to the drawings. FIG. 1 is a block diagram of a key telephone device according to an embodiment of the present invention.

In this embodiment, parts that are the same as those in the conventional example shown in FIG.

The feature of this embodiment is that a photocoupler 6 is used in place of the relay 5 of the conventional configuration, and a semiconductor switch element 7 is used in place of the relay contact 5a.

The photocoupler 6 includes a light emitting element 61 connected to the output terminal of the control circuit 4, a light receiving element 62 such as a phototransistor that receives light from the light emitting element 61 and flows a photocurrent,
It is composed of a transistor 63 for amplifying the output current of the light receiving element 62 and a diode 64 inserted between the corephthal emitter of the transistor 63. Further, as the semiconductor switch element 7, a transistor having a withstand capacity and a withstand voltage that allows line current to pass through without any problem can be used. Note that the semiconductor switch element 7 is PNP or NPN according to the output polarity of the diode bridge 2.
It is necessary to select a transistor.

The operation of the above configuration will be described below.

When a current flows between the output terminals of the control circuit 4, the light emitting element 61 of the photocoupler 6 emits light. When the light emitting element 61 emits light, the light receiving element 62 disposed opposite thereto receives the light and outputs a photoelectric conversion signal. The light-receiving element 62 is combined with a transistor 63 to form a Darlington circuit, and the output terminal of the light-receiving element 62 is connected to the CTR (Current) of the light-emitting element 61.
Transfer Ratio (current transfer ratio) times the current becomes the collector current of the transistor 63.

Furthermore, the collector current of the transistor 63 times hyt (common emitter current amplification factor) flows into the semiconductor switch element 7 .

Therefore, with respect to the communication current 1 flowing through the communication line, the current 1' (i.e., the output current of the control circuit 4) required to operate the semiconductor switch element 7 is 1'= 1/(CTR
X 1lpt). This value is extremely small compared to the current that should be passed through the excitation coil v-(D), and the current consumption for opening and closing the communication loop can be significantly reduced.

Effects of the Invention As described above, according to the present invention, a semiconductor switch element is inserted into the line between the office line and the communication circuit, and the photocoupler that drives the semiconductor switch element and the office line are electrically connected to each other. Since an insulated control circuit for controlling the photocoupler is provided, the communication loop can be opened and closed with low current consumption. Furthermore, since a photocoupler is smaller than a relay, the mounting area can be reduced.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing a key telephone device according to an embodiment of the present invention, and FIG. 2 is a block diagram showing an example of a conventional key telephone device. 1... Office line, 2... Diode bridge, 3...
Call circuit, 4... Control circuit, 6... Photocoupler,
7...Semiconductor switching element. Name of agent: Patent attorney Shigetaka Awano and 1 other person

Claims (1)

[Claims] A communication circuit connected to the office line, a semiconductor switch element inserted into a line connecting the communication circuit and the office line, a photocoupler that drives the semiconductor switch element, and an electrical connection to the office line. and a control circuit that is electrically insulated and controls the photocoupler.