JPH0233423Y2 - - Google Patents

Description

[Detailed description of the invention] [Field of industrial application] The present invention relates to a holding circuit for telephones, and is particularly applicable to so-called parent-child telephones in which multiple telephones are connected in parallel to a pair of office lines. The present invention relates to a holding circuit that has a function of automatically releasing from a state.

In general, so-called parent-child telephones have been proposed in which only one pair of office lines, that is, a single telephone line, is shared, and multiple telephones are connected in parallel to this pair of office lines so that they can be installed at separate locations. ing.

For example, in a certain house, if telephones are installed on the first and second floors and connected to a pair of office lines,
When answering an incoming call with the telephone installed on the first floor and re-answering with the telephone installed on the second floor, the telephone on the first floor should be disconnected from the handset, that is, kept in an off-hook state, and the telephone on the second floor should be kept in an off-hook state. Raise the handset,
That is, by going off-hook, it becomes possible to talk.

However, with this configuration, after ending a call on the telephone on the second floor, you must either lower the handset of the telephone on the first floor, that is, turn it on-hook, or raise the handset of the telephone on the second floor, that is, turn it off-hook. Unless the telephone on the second floor is turned on and the telephone on the second floor is used to make a call, the telephone on the first floor will not receive an incoming call after the call ends, which is a problem in terms of usability.

On the other hand, in order to solve this problem, a multifunctional telephone device known as a button telephone device has been proposed. This telephone device can be connected to one or more central office lines, and is equipped with a plurality of button telephones with a large number of push buttons arranged on the operation surface, and a main device for controlling these telephones. In addition to this function, it also performs functions such as holding a call during a call, and a so-called extension call function between multiple telephones connected via the main device. However, while this configuration can satisfactorily solve the above-mentioned problems with parent-child telephones, it requires a large number of complicated and expensive circuit parts, making the telephone device extremely expensive.

[Conventional technology]

Therefore, the present inventors filed an application for an invention with the same name as the present invention as Japanese Patent Application No. 91788 on May 10, 1988 (hereinafter, this application will be referred to as the "prior application"). In this earlier application, in a so-called parent-child telephone in which a plurality of telephones are connected in parallel to a pair of office lines, at least one of the telephones is provided with a polarity matching circuit in parallel to the office line, and the polarity matching circuit has a transistor and a silicon-controlled rectifier on the output side of the
The emitter and base of the transistor are connected via a first resistor, the base of the transistor is connected to one of the main electrode terminals of the silicon controlled rectifier, and one of the output terminals of the polarity matching circuit is connected to the silicon control rectifier. A second resistor and a first capacitor are connected in parallel between the other main electrode terminal of the rectifier, and a third resistor is connected between one of the output terminals of the polarity matching circuit and the collector of the transistor. A trigger circuit is provided on the output side of the polarity matching circuit for applying a trigger pulse to the gate of the silicon controlled rectifier via a switch, and the other output terminal of the polarity matching circuit and the light emitting diode are connected in series. A holding circuit with an automatic release function for a telephone is disclosed in which the emitter of the transistor is connected.

According to such a configuration, after answering an incoming call using the telephone equipped with the above-mentioned holding circuit with automatic release function,
Once the telephone is placed on hold, the telephone is put on hold, the handset is put down, and when the telephone is answered again using the telephone or another telephone, the telephone on hold can be automatically released from the hold. In addition, since a station line capture circuit consisting of a transistor, a third resistor, and a light emitting diode is provided, it is possible to display whether or not there is a hold state with the light emitting diode, and also to display the resistance value of the first resistor. It is possible to increase the current capacity and use a silicon-controlled rectifier with a small current capacity, making it possible to reduce the cost and size.

[Problem that the invention attempts to solve]

However, in the conventional configuration described above, the station line capture circuit is directly connected to the station line via the polarity matching circuit, that is, the other output terminal of the polarity matching circuit and the emitter of the transistor in the station line capture circuit are connected directly to the station line. This transistor is expensive because it requires a transistor with a high breakdown voltage that can withstand ringing. Furthermore, while on hold in the above-mentioned holding circuit with an automatic release function, an alternating current such as an audio signal current flows into the holding circuit with an automatic release function superimposed on the direct current, but this alternating current causes the current flowing to the silicon-controlled rectifier to be maintained. When the current becomes lower than that, the silicon-controlled rectifier is turned off, and the transistor in the station line capture circuit is also cut off, posing a risk that the holding state may be canceled by mistake.

[Means for solving problems]

In the present invention, the other output terminal of the polarity matching circuit and the emitter of the transistor are not directly connected to each other, but the output terminal of the polarity matching circuit is By connecting the switch and the coil of the relay in series between the emitter of the other transistor and the emitter of the transistor, and connecting the make contact of the relay in parallel with the switch, it is possible to eliminate disconnects the station line capture circuit from the station line,
Further, it is characterized in that it is possible to prevent the hold from being erroneously released.

〔Example〕

Next, embodiments of the present invention will be described in detail with reference to the drawings.

Referring to FIG. 1, a plurality of telephones TEL ₁ to TEL _o are connected in parallel to one central office line 1, and telephone TEL ₁ is equipped with an automatic release function according to an embodiment of the present invention. A reservation circuit 2 is provided.

The reservation circuit 2 with an automatic release function includes a polarity matching circuit 3 made of a bridge rectifier circuit including four diodes D ₁ to _{D 4} connected in parallel to the station line 1 . The output side of the polarity matching circuit 3 has a transistor _TR1 and a silicon-controlled rectifier SCR. The emitter and base of the transistor _TR1 are connected via a resistor, and the base is connected to the anode of a silicon-controlled rectifier SCR.
Negative terminal of polarity matching circuit 3 and silicon controlled rectifier
Resistor R ₂ and capacitor C ₁ between the cathode of SCR
are connected in parallel. Also, polarity matching circuit 3
A resistor ₃ and a light emitting diode LED are connected in series between the negative terminal of the transistor TR ₁ and the collector of the transistor TR 1, and a local line capture circuit 4 is constituted by the transistor TR ₁ , the resistor R ₃ , and the light emitting diode LED. .

At the output of the polarity match circuit 3, a trigger circuit 5 is provided for triggering the gate of the silicon-controlled rectifier SCR via a non-locking hold switch H. A coil COL of a self-holding relay RL is connected between the positive terminal of the polarity matching circuit 3 and the emitter of the transistor _TR1 via a non-locking holding switch H, and the self-holding relay RL is connected in parallel with the non-locking holding switch H. The make contact r1 of is connected. Further, in this embodiment, a resistor _R4 and a capacitor _C2 are connected in parallel between the negative terminal of the polarity matching circuit 3 and the emitter of the transistor _TR1 . Further, a hold tone sending circuit 6 is provided on the output side of the polarity matching circuit 3 via a make contact r1 of a self-holding relay RL. In addition,
L ₁ and L ₂ are office line terminals.

The trigger circuit 5 includes resistors R ₅ to R ₇ and a capacitor.
When the non-lock holding switch H is turned on, that is, closed, a voltage is applied to the capacitor _C3 through the switch H, and the differential waveform due to the capacitor _{C3 and} the resistor _R7 is A current triggers into the gate of the silicon controlled rectifier SCR through resistor _R5 .

The held music sending circuit 6 includes Darlington-connected transistors TR ₂ , TR ₃ , resistors R ₈ to _{R 11} , and a capacitor.
It consists of C ₄ , C ₅ and a well-known music-on-hold generation circuit MIC that generates music on hold. A voltage is applied to the held music sending circuit 6 only while the make contact of the self-holding relay RL is closed, that is, only during hold, and the held music is generated from the held music generating circuit MIC.

Next, the operation of the circuit shown in FIG. 1 will be explained.

When telephone TEL ₁ receives an incoming call and the telephone TEL 1 is to be placed on hold after answering the call, i.e., off-hooking the handset (not shown) of telephone TEL ₁ , the non-lock type hold switch H is turned on, ie, closed. By closing the non-lock type hold switch H, the DC power supply of the station line 1 is transferred to the polarity matching circuit 3 and the non-lock type hold switch H.
is applied to the capacitor _C3 of the trigger circuit 5 through the capacitor _C3 and the resistor _R7 , and the current with a differential waveform is applied to the silicon controlled rectifier SCR through the resistor _R5 .
Input the trigger to the gate. As a result, the silicon controlled rectifier SCR is turned on, and the direct current of the station line 1 is transferred from the station line terminal L ₁ to the polarity matching circuit 3, the non-lock type holding switch H, and the self-holding relay RL.
Coil COL, resistor R ₁ , silicon controlled rectifier
It flows through the path of SCR, resistor R ₂ , polarity matching circuit 3, and station line terminal L ₂ . When current flows through the coil COL of the self-holding relay RL, the make contact r1 of the self-holding relay RL is closed. Therefore, even if the non-lock type hold switch H is turned off or opened, the current continues to flow through the make contact r1 instead of the non-lock type hold switch H in the above-mentioned path.

Also, as the silicon controlled rectifier SCR is turned on, a current also flows to the base of the transistor TR ₁ , and the transistor TR ₁ is turned on, that is, becomes conductive, and the DC current of the station line 1 is transferred to the station line terminal L ₁ ,
Polarity matching circuit 3, make contact r1 of self-holding relay RL, coil COL, transistor TR ₁ , resistor R ₃ , light emitting diode LED, polarity matching circuit 3,
It also flows through the path of the central line terminal _L2 , and the central line 1 becomes trapped in this path.

In this state, by on-hooking the handset of the telephone TEL ₁ , the communication line resistance (not shown) of the telephone TEL ₁ , which was connected in parallel with the holding circuit 2 with automatic release function, that is, in parallel with the central office line 1, is ) is disconnected, and the voltage between station line terminals L ₁ and L ₂ increases.
Therefore, the charging voltage of capacitors C ₁ and C ₂ also increases.
Also, since the make contact r1 of the self-holding relay RL is closed, the hold tone sending circuit 6 generates the hold tone.

In this hold state, alternating current such as audio signal current superimposed on direct current flows into the hold circuit 2 with automatic release function, but this alternating current is blocked by coil COL of self-holding relay RL. ,
It is possible to prevent the current flowing through the silicon controlled rectifier SCR from falling below the holding current. Furthermore, even if some alternating current leaks because it cannot be sufficiently blocked by the coil COL of the self-holding relay RL, this leaked alternating current is bypassed by the capacitor _C2 .

Next, when you take off the handset (not shown) of telephone TEL ₁ , i.e., answer again, telephone TEL ₂
The communication line resistance (not shown) and the hold circuit 2 with automatic release function are connected in parallel, and the station line terminals L ₁ , L ₂
The voltage between them drops. At that time, the charging voltage of the capacitor C ₂ becomes temporarily higher than the voltage between the station line terminals L ₁ and L ₂ , but the charge stored in the capacitor C ₂ causes the charging voltage to rise between the station line terminals L ₁ and L _{2 .} It is instantaneously discharged through resistor _R4 etc. in the direction equal to the voltage between the two. Note that the time constant τ ₂ = R 4 C ₂ defined by resistor R ₄ and capacitor C ₂ is smaller than the time constant τ ₁ = R ₂ C ₁ defined by resistor R ₂ and capacitor C _{1 .} Then, due to the discharge of capacitor C ₂ ,
The charging voltage of the capacitor _C1 becomes higher than the voltage between the anode of the silicon-controlled rectifier SCR and the negative terminal of the polarity matching circuit 3, and the current flowing through the silicon-controlled rectifier SCR becomes less than its holding current, so that the current flowing through the silicon-controlled rectifier SCR becomes lower than its holding current. turns off.

When the silicon controlled rectifier SCR turns off,
Since the base current of the transistor TR ₁ stops flowing, the transistor TR ₁ is also turned off, ie, is in a cutoff state, and the station line capture circuit 4 is no longer able to capture the station line, that is, the pending state is released. At the same time, current no longer flows through the coil COL of the self-holding relay RL, its make contact r1 is opened, and the held music sending circuit 6 stops generating the held music.

In this way, the power from the station line 1 is applied to the station line acquisition circuit 4 via the polarity matching circuit 3 only in the hold state by the self-holding relay RL. It is not necessary to use an expensive transistor with a high breakdown voltage that can withstand ringing as the transistor _TR1 of the line capture circuit 4.

In addition, in the operation explanation of the above embodiment, the telephone
After answering the call with TEL ₁ , the call will be put on hold,
We have described an example in which the hold state of telephone TEL ₁ is automatically released when the handset of telephone TEL ₁ is lowered and the handset of telephone TEL ₂ is raised to _answer again. Even if you pick up the handset of TEL _o , the hold status of telephone TEL ₁ can be automatically released. Further, it goes without saying that this holding circuit with an automatic release function may be internally installed in the telephones TEL ₂ to TEL _o .

Further, in the above embodiment, a pnp type transistor is used as the transistor _TR1 of the central line capture circuit 4, but an npn type transistor may also be used. An example is shown in FIG.

To put it simply, the holding circuit with automatic release function shown in FIG. 2 reverses the polarity of the polarity matching circuit 3 explained in FIG. cathode)
are connected in reverse. The operation of the circuit shown in FIG. 2 can be easily inferred from the operation of the circuit shown in FIG. 1, so a description thereof will be omitted.

[Effect of idea]

As is clear from the above explanation, according to the present invention, since the station line acquisition circuit is disconnected from the station line except during the hold operation, ringing does not occur in the transistor of the station line acquisition circuit. There is no need to use expensive transistors with high withstand voltages, and inexpensive transistors can be used.

Also, while the current is on hold, the coil of the self-holding relay prevents the alternating current superimposed on the direct current from flowing into the silicon-controlled rectifier, and the leaked alternating current that cannot be blocked by the coil is bypassed with a capacitor. , the current flowing through the silicon-controlled rectifier can be prevented from dropping below its holding current, thus preventing the hold from being erroneously released.

Furthermore, it is desirable that the direct current resistance during acquisition of a pending station line be as small as possible, and for this reason, the coil of the self-holding relay is convenient.

[Brief explanation of the drawing]

Fig. 1 is a circuit diagram showing the configuration of one embodiment of the holding circuit with automatic release function according to the present invention, and Fig. 2 is a circuit diagram showing the structure of another embodiment of the holding circuit with automatic release function according to the present invention. It is a diagram. 1...Station line, 2...Holding circuit with automatic release function,
3...Polarity matching circuit, 4...Station line acquisition circuit, 5...
...Trigger circuit, 6...Hold tone sending circuit, RL...
Self-holding relay, H...Non-lock switch, _R1 , _R2 , _R4 ...Resistor, SCR...Silicon control rectifier, _C1 , _C2 ...Capacitor, TEL ₁ ~
TEL _o ...Telephone.

Claims (1)

[Scope of claim for utility model registration] 1. Multiple telephones (TEL ₁
~TEL _o ) connected in parallel, at least one of the telephones is provided with a polarity matching circuit 3 in parallel with the central office line,
A transistor _TR1 is connected to the output side of the polarity matching circuit.
and a silicon controlled rectifier SCR, connecting the emitter and base of the transistor to a first resistor.
_R1 , connecting the base of the transistor and one of the main electrode terminals of the silicon-controlled rectifier, and between one of the output terminals of the polarity matching circuit and the other of the main electrode terminals of the silicon-controlled rectifier. the second resistor R ₂ and the first codenser C ₁
are connected in parallel, a third resistor R3 and a light emitting diode LED are connected in series between one of the output terminals of the polarity matching circuit and the collector of the transistor, and a third resistor _R3 and a light emitting diode LED are connected in series between one of the output terminals of the polarity matching circuit and the collector of the transistor. A trigger circuit 5 is provided for applying a trigger pulse to the gate of the silicon controlled rectifier via a switch H, and a relay RL is provided via the switch between the other output terminal of the polarity matching circuit and the emitter of the transistor. A fourth resistor _R4 and a second resistor are connected between one of the output terminals of the polarity matching circuit and the emitter of the transistor. A telephone holding circuit with an automatic release function, characterized by connecting a capacitor _C2 in parallel. 2. A holding circuit with an automatic release function for a telephone according to claim 1, wherein a holding tone sending circuit 6 is provided on the output side of the polarity matching circuit via the make contact of the relay.