JPS6236424B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a communication current supply circuit for key telephones and the like.

In general telephones, the direct current supplied from the exchange is interrupted by a hook switch or a dial, and by monitoring the intermittence of the direct current at the exchange, it is possible to detect call origination, answer, and end of the call, and dial/receive. Pulses are being received.

On the other hand, there are button telephone devices that allow multiple subscribers to share one to 10 lines with two to 20 telephones, and also allow extension calls between these telephones. In multi-function terminals that are housed in private branch exchanges and provide a variety of advanced services through the operation of buttons or blinking lamps, the DC loop with the exchange is always closed by a transmitter, etc. inside the terminal. In some cases, a system is used in which the hook switch information and dial information are transmitted through a line separately provided between the terminal and the exchange.

If a supply circuit conventionally used in general telephones is used to supply talk current to such key telephones, the talk current will continue to flow even to idle key telephones, which is extremely inconvenient. It's the economy.

SUMMARY OF THE INVENTION An object of the present invention is to provide a communication current supply circuit that does not allow communication current to flow to a button telephone in an idle state, thereby eliminating wasteful power consumption.

According to the present invention, a DC current is applied to a terminal in which a DC path is always formed between terminals A and B internally, and which transmits at least call information to an exchange via a signal line different from a communication line. a direct current supply circuit that supplies a direct current between terminals A and B of the terminal, and a direct current supply circuit that is inserted between terminals A and B of the terminal and the incoming line of the exchange. an AC coupling circuit, a monitoring circuit that is connected to the incoming line of the exchange and detects the voltage or current of the incoming line, and turns on/off the DC current supply circuit based on the output of the monitoring circuit or a power supply request signal supplied from the exchange. A communication current supply circuit comprising means for controlling off is obtained.

Next, the present invention will be explained with reference to the drawings.

FIG. 1 is a diagram showing an example of a conventional communication current supply circuit.

As shown in FIG. 1, when a small current, low withstand voltage semiconductor switch such as a silicon controlled rectifier (hereinafter referred to as SCR) 101 is used as a switch element in a communication path 100, a conventional mechanical contact is used. Unlike an exchange, it is not possible to supply telephone current to the telephone 102 through the telephone line 100. Therefore, in such an all-electronic exchange, a transformer 1 for blocking DC current is installed in the subscriber circuit 103.
04 is provided and the communication current is supplied from the subscriber circuit 103. In FIG. 1, the communication current is supplied to the telephone 102 by the storage battery 1
05, the current detection circuit 106 - the first resistor 107 - the first winding 108 of the transformer 104 - the telephone 102 - the second winding 109 of the transformer 104 - the second resistor 11
0 - This is done in the path of the negative terminal of the storage battery 105. Here, the contact point 11 of the telephone 102 is activated by turning on/off the handset, dialing, etc.
1, the communication current is interrupted, and by monitoring the interruption of the communication current by the current detection circuit 106, the subscriber makes a call.
It is capable of answering, detecting end of call, and receiving dial pulses. As shown in FIG. 1, in a general telephone 102, when the telephone 102 is not in use, the contact 111 is always kept open, so that no current flows through the contact 111. Note that the electricity storage device 11
Reference numeral 2 is for blocking direct current of communication current.

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

According to FIG. 2, the subscriber circuit 1 shown in FIG.
03, the first and second terminals 200,
201 is selectively connected to either receiver 203 or speaker 204 by hook switch 202 . In FIG. 2, the handset 203 is turned on.
In the hooked state, the first terminal and the second terminal 200 and 201 are connected to the handset 203, and the handset 203 is supplied with talking current. On the other hand, when the handset 203 is on-hook, the communication current from the subscriber circuit 103 shown in FIG. - the second winding 208 of the transformer 205 - the switch 202 - the second terminal 201, and thereby the amplifier 207
Power is supplied to the At this time, the audio signal from the subscriber 103 shown in FIG.
In the key telephone as shown in FIG. 2, the DC loop is closed both when the handset 203 is in the on-hook state and in the off-hook state, so the current detection circuit 106 as shown in FIG. It is not possible to monitor the state of the button telephone's hook switch 202. For this reason, in the button telephone shown in FIG. 2, switch information, dial information, etc. are sent to the exchange through a data line 209 provided separately. In this way, in a button telephone as shown in FIG.
Since the DC loop is always closed regardless of the state of This is very uneconomical because current is supplied. Furthermore, the second
In the figure, a capacitor 210 blocks direct current.

FIG. 3 is a diagram showing an embodiment of the present invention.

Referring to FIG. 3, an embodiment of the invention provides a button telephone 300 with respective first and second windings 108.
and a transformer 104 connected to one end of the first and second windings 108 and 109 of the transformer 104, and a first DC blocking capacitor 112 and a first DC blocking capacitor 112 having both ends connected to the other ends of the first and second windings 108 and 109 of the transformer 104, respectively. a first resistor 107 whose one end is connected to the other end of the first winding 108 of the first resistor 104;
7 and the second winding 10 of the transformer 104 and the switch element 301 whose one end is connected to the ground, respectively.
a second resistor 110 having one end connected to the other end of 9;
A storage battery 10 with a negative terminal and a positive terminal connected to the other end of this second resistor, respectively.
5 and a second DC blocking capacitor 30 inserted between one end of the third winding 302 of the transformer 104 and the earth.
3 and one end of the third winding 302 of the transformer 104 and +
Current detection circuit 304 inserted between the 12V power supply
and an OR circuit 305, which has one input connected to the output of the current detection circuit 304 and the other input connected to a central processing circuit (not shown), and which controls opening and closing of the switch element 301 based on the output. . In FIG. 3, both hook switch information and dial information from key telephone 300 are transmitted through data line 209 to a central processing circuit (not shown). Based on this information, the central processing circuit controls the opening and closing of the SCR 101 of the communication path 100 to provide a conversion service to the subscriber of the key telephone 300. At this time, in order to maintain the conduction state of the SCR 101, it is necessary to flow a DC current higher than a certain specified current, and the DC current for this purpose (hereinafter referred to as the holding current) is supplied to the third winding of the SCR 101-transformer 104. In the path of line 302-current detection circuit 304
Flows into the 12V power supply. Here, the current detection circuit 304
monitors the opening and closing of SCR101 by detecting the presence or absence of holding current in SCR101,
The switch element 301 is controlled through an OR circuit 305 so that the switch element 301 is closed when the signal 1 is in a conductive state. As a result, the supply of communication current to the key telephone 300 is not performed when the SCR 101 is opened, and it is possible to prevent unnecessary current from flowing when the key telephone 300 is not in use. At this time, the communication current to the button telephone 300 is
5 to the ground - switch element 301 - first resistor 107 - first winding 108 of transformer 104 -
Button telephone 300 - second winding 1 of transformer 104
09-Second resistor 110--The negative terminal of the storage battery 105 is supplied.

Further, in the circuit example of the button telephone shown in FIG. 2, an example is shown in which the communication current is supplied to the handset 203 and the amplifier 207, but it may also be used for other purposes such as lighting a lamp. In such a case, power supply to the button telephone 300 may be required even when the SCR 101 shown in FIG. 3 is not in a conductive state. Therefore, in Fig. 3, the current detection circuit 3
An OR circuit 305 is provided so that opening/closing control of the switch element 301 can be performed by both the switch element 04 and a central processing circuit (not shown).

As described above, according to the present invention, a communication current supply circuit without unnecessary power consumption can be obtained.

[Brief explanation of the drawing]

Fig. 1 is a diagram showing an example of a conventional telephone current supply circuit, Fig. 2 is a diagram showing an example of a button telephone circuit, and Fig. 3 is a diagram showing an example of a conventional telephone current supply circuit.
The figure shows an embodiment of the present invention. In the figure, 101 is SCR, 104 and 2
06 is a transformer, 105 is a storage battery, 106 and 3
04 is a current detection circuit, 107 and 110 are resistors, 112, 210 and 303 are capacitors, 20
2 is a hook switch, 204 is a speaker, 20
3 represents a handset, 207 an amplifier, 300 a button telephone, 301 a switch element, and 305 an OR circuit.

Claims (1)

[Claims] 1 A telephone current that supplies direct current to a terminal in which a direct current path is always formed between terminals A and B internally and which transmits at least call information to the exchange via a signal line separate from the telephone line. a DC current supply circuit that supplies a DC current between terminals A and B of the terminal; and terminal A of the terminal;
an AC coupling circuit inserted between B and the incoming line of the exchange; a monitoring circuit connected to the incoming line of the exchange to detect the voltage or current of the incoming line; and means for controlling on/off of the DC current supply circuit based on a power supply request signal.