JPH0580076U - Telephone interface circuit and telephone device - Google Patents

Abstract

(57) [Abstract] [Purpose] A telephone interface that prevents collapse of impedance matching on the secondary winding t2 side of the transformer 13 when the telephone 10 changes from an off-hook state to an on-hook state and prevents howling to the other party. Circuit provision. The impedance on the secondary winding t2 side of the transformer 13 when the telephone 10 is changed from the off-hook state to the on-hook state is connected between both ends of the secondary winding t2 of the transformer 13, and the primary winding of the transformer 13 An impedance matching circuit having a Zener diode for impedance matching with the impedance on the t1 side is provided.

Description

[Detailed description of the device]

[0001]

[Industrial applications]

 The present invention relates to a telephone interface circuit connected between at least one telephone and at least one communication path. The present invention further relates to a telephone device having the telephone and the telephone interface circuit.

[0002]

[Prior Art]

 2. Description of the Related Art Conventionally, as shown in FIG. 2, a telephone device of this type (a button telephone device in the illustrated example) has at least one telephone (single telephone in the illustrated example) 10 and at least one telephone call with the telephone 10. A telephone line interface circuit 12 connected to a telephone line (three communication channels 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 speech path switch (XP-SW) 14 is connected to the speech path 11 and one end of the primary winding t1 of the transformer 13, receives the on / off control signal C, and when the on / off control signal C indicates connection on. Is connected between the communication path 11 and the primary winding t1 of the transformer 13, and 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 established. Turn off. The transformer 13 separates the telephone 10 and the communication path 11 from each other in a direct current manner. The DC superimposing circuit 15 is connected to both ends of the secondary winding t2 of the transformer 13 and acts as a current supply circuit for supplying a call current to the telephone 10 when the telephone 10 is in the off-hook state. The telephone 10 has a call circuit 16 and a hook switch HS. The hook switch HS is in the on-hook state in the illustrated state. The DC superimposing circuit 15, the communication circuit 16, and the hook switch HS form a loop. When the hook switch HS is in the off-hook state, the loop becomes a closed loop, and when the hook switch HS is in the on-hook state, the loop is opened. It becomes a loop (loop break).

The loop detection circuit 17 detects the disconnection of the loop (that is, the on-hook of the telephone 10) and the closing of the loop (that is, the off-hook of the telephone 10), and outputs an on-hook detection signal and an off-hook detection signal, respectively. Output. In response to the off-hook detection signal, the control unit 18 outputs an on / off control signal C indicating that the connection is on, and causes the speech path switch 14 to connect between the speech path 11 and the primary winding t1 of the transformer 13. Connect. In addition, the control unit 18 outputs an on / off control signal C indicating connection off in response to the on-hook detection signal, and causes the call path switch 14 to connect the call path 11 and the primary winding t1 of the transformer 13. Disconnect the connection between

[0005]

[Problems to be solved by the device]

 In this way, when the telephone set 10 changes from the off-hook state to the on-hook state, the loop detection section 17 detects the on-hook state, and the control section 18 responds to the on-hook detection signal by instructing the call path switch 14 to indicate the call path 11 And the primary winding t 1 of the transformer 13 are disconnected. At this time, at the moment when the telephone 10 changes from the off-hook state to the on-hook state, the impedance of 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 broken. The state in which the impedance matching is broken continues until the call path switch 14 disconnects the connection between the call path 11 and the primary winding t1 of the transformer 13. When the impedance matching is broken, howling is heard by the other party who is talking on the communication path 11.

An object of the present invention is to provide a telephone interface circuit capable of preventing impedance matching collapse on the transformer secondary winding side 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 capable of preventing collapse of impedance matching on the secondary winding side of the transformer when the telephone is changed from the off-hook state to the 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 communication path, the telephone interface circuit having a primary winding and a secondary winding. Connected to the speech path and the primary winding of the transformer. When an on-off control signal is received and the on-off control signal indicates connection on, the communication path and the transformer are connected. A speech path switch which is connected to the primary winding and disconnects the speech path from 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 to supply a call current to the telephone when the telephone is in an off-hook state, and detecting on-hook and off-hook of the telephone, Detecting means for outputting an off-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, and the connection in response to the off-hook detection signal. In a telephone interface circuit having a control section for outputting the on / off control signal indicating ON, when the telephone is connected between both ends of the secondary winding of the transformer and the telephone changes from an off-hook state to an on-hook state. A telephone interface circuit having an impedance matching circuit that impedance-matches the impedance of the transformer on the secondary winding side with the impedance of the transformer on the primary winding side.

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 is A transformer having a primary winding and a secondary winding, and connected to the communication path and the primary winding of the transformer, receiving an on / off control signal, and the on / off control signal indicating connection on, Connecting the speech path and the primary winding of the transformer, and when the on / off control signal indicates connection off, connect the speech path and the primary winding of the transformer. A call path switch to be turned off and a current supply circuit that is connected to both ends of the secondary winding of the transformer and supplies a call current to the telephone when the telephone is off-hook. And a 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 in response to the on-hook detection signal, outputting the on-off control signal indicating the connection off A telephone unit having a control unit that outputs the on / off control signal indicating the connection on in response to the off-hook detection signal, the telephone interface circuit includes: Impedance matching of the impedance on the secondary winding side of the transformer when the telephone changes from the off-hook state to the on-hook state is connected to the impedance on the primary winding side of the transformer, which is connected between both ends of the line. There is provided a telephone device having an impedance matching circuit for controlling.

The impedance matching circuit preferably includes a Zener diode connected across the secondary winding of the transformer.

[0011]

【Example】

 Next, an embodiment of the present invention will be described with reference to the drawings.

Referring to FIG. 1, a telephone device according to an embodiment of the present invention includes the same parts as those of FIG. 2 indicated by the same reference numerals. In this telephone device, the telephone interface circuit 12 has a series connection circuit of a Zener diode ZD and a resistor R connected between both ends of a secondary winding t2 of a transformer 13. This series connection circuit is an impedance matching circuit that impedance-matches the impedance on the secondary winding t2 side of the transformer 13 when the telephone 10 changes from the off-hook state to the on-hook state to the impedance on the primary winding t1 side of the transformer 13. Acts as. The Zener diode ZD detects a voltage rise due to the on-hook of the telephone set 10, matches impedance, and prevents howling to the other party.

[0013]

[Effect of the device]

 According to the present invention, it is possible to prevent the impedance matching collapse on the secondary winding side of the transformer when the telephone changes from the off-hook state to the on-hook state, and thus to prevent the howling to the communication partner. can get.

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

[Brief description of 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]

 10 Telephone 11 Speech Channel 12 Telephone Interface Circuit 13 Transformer 14 Speech Channel Switch 15 DC Superimposition Circuit 17 Loop Detection Circuit 18 Control Section ZD Zener Diode R Resistance

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Hiroshi Sakaino 1-6, 1-chome, Saiwaicho, Chiyoda-ku, Tokyo Nihon Telegraph and Telephone Corporation

Claims (4)

[Scope of utility model registration request] 1. A telephone interface circuit connected between at least one telephone and at least one speech path, the transformer having a primary winding and a secondary winding, and the speech path and the transformer. When connected to the primary winding and receiving an ON / OFF control signal, and the ON / OFF control signal indicates that the connection is ON, the speech path and the primary winding of the transformer are connected to perform the ON / OFF control. When the signal indicates connection off, a speech path switch for disconnecting the connection between the speech path and the primary winding of the transformer, and connected to both ends of the secondary winding of the transformer, When the telephone is off-hook, a current supply circuit for supplying a call current to the telephone and an on-hook and off-hook of the telephone are detected to detect an on-hook detection signal and an off-hook detection signal. Detecting means for respectively outputting a signal, and in response to the on-hook detection signal, outputs the on-off control signal indicating the connection off, and in response to the off-hook detection signal, the on-off control signal indicating the connection on. In a telephone interface circuit having a control section for outputting, the secondary winding side of the transformer is connected between both ends of the secondary winding of the transformer, and when the telephone changes from an off-hook state to an on-hook state. A telephone interface circuit having an impedance matching circuit for matching impedance with impedance on the primary winding side of the transformer. 2. The telephone interface circuit according to claim 1, wherein the impedance matching circuit includes a Zener diode connected across the secondary winding of the transformer. 3. A telephone device comprising at least one telephone and a telephone interface circuit connected between the telephone and at least one speech path, the telephone interface circuit comprising a primary winding and a secondary winding. When the on / off control signal is connected to the transformer having a secondary winding, the speech path and the primary winding of the transformer, and the on / off control signal indicates connection on, the speech path and the A speech path switch that connects between the primary winding of the transformer and disconnects the connection between the speech path and the primary winding of the transformer when the on / off control signal indicates connection off. A current supply circuit that is connected to both ends of the secondary winding of the transformer and supplies a call 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 in response to the on-hook detection signal, outputting the on-off control signal indicating the connection off, the off-hook A telephone device having a control unit that outputs the ON / OFF control signal indicating the connection ON in response to a 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 impedance-matches the impedance on the secondary winding side of the transformer with the impedance on the primary winding side of the transformer when the telephone changes from the off-hook state to the on-hook state. Telephone equipment. 4. The telephone device according to claim 3, wherein the impedance matching circuit includes a Zener diode connected across the secondary winding of the transformer.