JP2587408Y2 - Telephone interface circuit and telephone device - Google Patents

Description

[Detailed description of the invention]

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a telephone interface circuit connected between at least one telephone and at least one communication channel. The present invention further relates to a telephone device having the telephone and the telephone interface circuit.

[0002]

2. Description of the Related Art Conventionally, this type of telephone device (key telephone device in the illustrated example) includes at least one telephone (single telephone in the illustrated example) 10 as shown in FIG. A telephone interface circuit 12 connected to at least one communication path (three communication paths in the illustrated example) 11;

The telephone interface circuit 12 has a transformer 13 having a primary winding t1 and a secondary winding t2. The communication path switch (XP-SW) 14 is connected to the communication path 11
Is connected to one end of the primary winding t1 of the transformer 13 and receives the on / off control signal C. When the on / off control signal C indicates connection ON, the communication path 11 and the primary winding t1 of the transformer 13 are connected to each other. When the ON / OFF control signal C indicates connection OFF, the connection between the communication path 11 and the primary winding t1 of the transformer 13 is disconnected. The transformer 13 is
The telephone 10 and the communication path 11 are DC-separated. The DC superimposing circuit 15 is connected to both ends of the secondary winding t2 of the transformer 13, and when the telephone 10 is in the off-hook state, the telephone 1
It functions as a current supply circuit that supplies a talk current to 0. The telephone 10 has a communication circuit 16 and a hook switch HS. The hook switch HS is in an on-hook state in the illustrated state. The DC superposition circuit 15, the communication circuit 16, and the hook switch HS form a loop. When the hook switch HS is in an off-hook state, the loop is a closed loop, and when the hook switch HS is in an on-hook state, the loop is opened. Loop break).

The loop detecting circuit 17 detects the break of the loop (ie, the on-hook of the telephone 10) and the closing of the loop (ie, the off-hook of the telephone 10), and outputs an on-hook detection signal and an off-hook detection signal, respectively. . The controller 18 outputs an on / off control signal C indicating connection ON in response to the off-hook detection signal, and causes the communication path switch 14 to connect the communication path 11 and the primary winding t1 of the transformer 13. . Also, the control unit 18
In response to the on-hook detection signal, an on / off control signal C indicating connection off is output, and the communication path switch 14 disconnects the connection between the communication path 11 and the primary winding t1 of the transformer 13.

[0005]

[Problem to be solved by the invention]
When 0 changes from the off-hook state to the on-hook state,
The loop detecting unit 17 detects the on-hook and the control unit 18
Responds to the on-hook detection signal, and
4 causes the connection between the communication path 11 and the primary winding t1 of the transformer 13 to be disconnected. At this time, at the moment when the telephone 10 changes from the off-hook state to the on-hook state, the impedance on the secondary winding t2 side of the transformer 13 becomes infinite, and the impedance matching with the primary winding t1 side of the transformer 13 is lost. The state of the misalignment continues until the communication path switch 14 disconnects the connection between the communication path 11 and the primary winding t1 of the transformer 13. In a state where the impedance matching is lost, howling can be heard by the other party on the call via the communication path 11.

An object of the present invention is to provide a telephone interface circuit which can prevent the impedance matching on the transformer secondary winding from being lost when the telephone changes from an off-hook state to an on-hook state.

Another object of the present invention is to provide a telephone device which can prevent the impedance matching on the transformer secondary winding from being lost when the telephone changes from an off-hook state to an on-hook state.

[0008]

According to the present invention, there is provided a telephone interface circuit connected between at least one telephone and at least one call path, the transformer having a primary winding and a secondary winding. A connection between the communication path and the primary winding of the transformer, receiving an on / off control signal, and when the on / off control signal indicates connection on, the communication path and the primary winding of the transformer. And a communication path switch for disconnecting the communication path from the primary winding of the transformer when the on / off control signal indicates connection off; and A current supply circuit connected to both ends of a secondary winding for supplying a talk current to the telephone when the telephone is in an off-hook state, detecting an on-hook and an off-hook of the telephone, and Detection means for outputting a hook detection signal and an off-hook detection signal, respectively, in response to the on-hook detection signal, outputting the on-off control signal indicating the connection off, and responding to the off-hook detection signal to turn on the connection on. And a control unit that outputs the on / off control signal shown in the figure, wherein the interface is connected between both ends of the secondary winding of the transformer, and the transformer of the transformer when the telephone changes from an off-hook state to an on-hook state. An impedance matching circuit for matching the impedance of the secondary winding to the impedance of the primary winding of the transformer, wherein the impedance matching circuit is connected between both ends of the secondary winding of the transformer. Telephone interface characterized by including a zener diode Scan circuit can be obtained.

Further, according to the present invention, there is provided a telephone device having at least one telephone and a telephone interface circuit connected between the telephone and at least one communication path, wherein the telephone interface circuit comprises: A transformer having a primary winding and a secondary winding, connected to the communication path and the primary winding of the transformer, receiving an on / off control signal, and when the on / off control signal indicates connection on, A connection is made between the communication path and the primary winding of the transformer, and when the on / off control signal indicates connection off, the connection between the communication path and the primary winding of the transformer is disconnected. A call path switch, and a current supply circuit connected to both ends of the secondary winding of the transformer and supplying a call current to the telephone when the telephone is in an off-hook state, Detecting means for detecting an on-hook and an off-hook of the telephone and outputting an on-hook detection signal and an off-hook detection signal, respectively, and outputting the on-off control signal indicating the connection off in response to the on-hook detection signal; In response to the detection signal,
A control unit that outputs the on / off control signal indicating the connection on, wherein the telephone interface circuit is connected between both ends of the secondary winding of the transformer, and the telephone is in an off-hook state. From an on-hook state to an impedance matching circuit for matching the impedance of the secondary winding of the transformer to the impedance of the primary winding of the transformer. And a Zener diode connected between both ends of said secondary winding.

[0010]

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described below with reference to the drawings.

Referring to FIG. 1, a telephone device according to one embodiment of the present invention includes the same parts indicated by the same reference numerals as the telephone device of FIG. In this telephone device, the telephone interface circuit 12 includes a secondary winding t2 of a transformer 13.
And a series-connected circuit of a Zener diode ZD and a resistor R connected between both ends of the resistor. This series connection circuit is an impedance matching circuit that matches the impedance of the secondary winding t2 of the transformer 13 when the telephone 10 changes from the off-hook state to the on-hook state to the impedance of the primary winding t1 of the transformer 13. It works. The zener diode ZD detects a voltage rise due to the on-hook of the telephone set 10, matches impedances, and prevents howling to the other party.

[0013]

According to the present invention, the impedance matching on the secondary winding side of the transformer when the telephone changes from the off-hook state to the on-hook state can be prevented.
A telephone interface circuit that can prevent howling to the other party can be obtained.

Further, according to the present invention, it is possible to prevent the impedance matching on the secondary winding side of the transformer from being disrupted when the telephone changes from the off-hook state to the on-hook state, and thus to prevent howling to the other party. A device is obtained.

[Brief description of the drawings]

FIG. 1 is a block diagram of a telephone device according to an embodiment of the present invention.

FIG. 2 is a block diagram of a conventional telephone device.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Telephone 11 Communication path 12 Telephone interface circuit 13 Transformer 14 Communication path switch 15 DC superposition circuit 17 Loop detection circuit 18 Control part ZD Zener diode R Resistance

──────────────────────────────────────────────────続 き Continuation of the front page (72) Inventor Hiroshi Sakaino Nippon Telegraph and Telephone Corporation, 1-6-1, Uchisaiwaicho, Chiyoda-ku, Tokyo (56) References JP-A-63-27194 (JP, A) JP-A Sho JP-A-2-266788 (JP, A) JP-A-60-247394 (JP, A) JP-A-61-108252 (JP, A) JP-A-60-197092 (JP, A) A) (58) Field surveyed (Int. Cl. ⁶ , DB name) H04Q 3/42-3/42 107 H04M 19/00-19/08

Claims (2)

(57) [Scope of request for utility model registration] 1. A telephone interface circuit connected between at least one telephone and at least one call path, comprising: a transformer having a primary winding and a secondary winding; Connected to the primary winding, receiving an on / off control signal, and when the on / off control signal indicates connection on, connecting between the communication path and the primary winding of the transformer; When the signal indicates connection off, a communication path switch that disconnects the connection between the communication path and the primary winding of the transformer, and is connected to both ends of the secondary winding of the transformer, A current supply circuit for supplying a call current to the telephone when the telephone is in an off-hook state; an on-hook detection signal and an off-hook detection signal for detecting on-hook and off-hook of the telephone; In response to the on-hook detection signal, outputs the on-off control signal indicating the connection-off, and responds to the off-hook detection signal in response to the on-off control signal indicating the connection on. A telephone interface circuit having a control unit for outputting a signal, wherein the terminal is connected between both ends of the secondary winding of the transformer, and the secondary winding side of the transformer when the telephone changes from an off-hook state to an on-hook state. An impedance matching circuit for matching the impedance to the impedance of the primary winding of the transformer, wherein the impedance matching circuit includes a Zener diode connected between both ends of the secondary winding of the transformer. A telephone interface circuit. 2. A telephone device comprising: at least one telephone; and a telephone interface circuit connected between the telephone and at least one communication channel, wherein the telephone interface circuit comprises a primary winding and a secondary winding. A transformer having a secondary winding, connected to the communication path and the primary winding of the transformer, receiving an on / off control signal, and when the on / off control signal indicates connection on, the communication path and the A communication path switch for connecting between the primary winding of the transformer and the connection between the communication path and the primary winding of the transformer when the on / off control signal indicates connection off. A current supply circuit connected to both ends of the secondary winding of the transformer, and for supplying a talk current to the telephone when the telephone is in an off-hook state;
Detecting means for detecting on-hook and off-hook of the telephone and outputting an on-hook detection signal and an off-hook detection signal, respectively, and outputting the on-off control signal indicating the connection off in response to the on-hook detection signal, A control unit that outputs the on / off control signal indicating the connection on in response to the detection signal, wherein the telephone interface circuit is connected between both ends of the secondary winding of the transformer. And an impedance matching circuit that matches the impedance of the secondary winding of the transformer when the telephone changes from the off-hook state to the on-hook state with the impedance of the primary winding of the transformer. An impedance matching circuit is provided for the secondary winding of the transformer. Telephone apparatus which comprises a zener diode connected between the end.