JPH0347795B2 - - Google Patents

Description

Detailed Description of the Invention (Industrial Application Field) The present invention relates to connecting a plurality of telephones or telephones with additional equipment in parallel to a telephone line (hereinafter referred to as central office line) from a central office exchange to a terminal telephone of a subscriber's telephone. The present invention relates to an automatic hold release device provided in a parent-child telephone device, etc.

(Prior Art) In conventional parent-child telephone devices, the holding operation and release are performed mechanically or even if they are electronic, they use a power source provided in the device rather than a central power source.

In the case of a mechanical method, in order to receive a transfer from another transferee's phone, the transferred party must lift the handset and press a button to release the hold, and even in the case of an electronic method, the call is released from hold. Although it was possible to release a call from hold by simply lifting the handset on the telephone itself, it was not possible to release a call from hold by simply lifting the handset on a telephone other than the telephone that was placed on hold.

(Problems to be Solved by the Invention) In such a parent-child telephone device, when only one person operates the telephone, the transfer operation is extremely troublesome.

For example, if a person who has been talking by raising the handset of a telephone installed on the first floor due to an incoming call wants to continue the conversation using a telephone installed on the second floor in order to view materials, etc., the person raising the handset of the telephone installed on the first floor may I had to go to the second floor, pick up the handset of the transferred phone, return to the first floor, lower the handset of the transferred phone, and then go back to the second floor and resume communication with the central office line.
Even if you did not perform this troublesome operation and made a call using the transferred telephone on the second floor while raising the handset of the transmitting telephone on the first floor, you could not make a satisfactory call because the sensitivity decreased.

The purpose of the present invention is to solve the above-mentioned drawbacks, and to provide a parent-child telephone that uses a small semiconductor switching element and a capacitor to release the hold by simply lifting the handset of the transmitting or transferred telephone. An object of the present invention is to provide an automatic device hold release device.

(Means for solving the problem) In a parent-child telephone device configured by connecting a plurality of telephones in parallel to a central office line, between at least one telephone or a central office line in a device attached to the telephone,
It has a semiconductor switching element having a self-holding function and a capacitor that is charged by the voltage between the station lines when the semiconductor switching element is conductive.

When the local office line is to be held, the semiconductor switching element having the self-holding function is triggered to conduct, thereby forming a holding loop for the local line. At this time, the capacitor is charged by the voltage between the station lines when the holding loop is closed. The electric charge in the capacitor is discharged by the voltage drop between the office lines due to the handset of the telephone on the transmitting side or the receiving side being lifted up. This discharge releases the self-holding of the semiconductor switching element having the self-holding function, and the DC closing circuit for holding is released.

(Function) To transfer calls, all you have to do is press the call switch on the telephone that connects the central office line.
Even if you keep the handset of the transferring phone up,
You can lower it again. There is no special operation required on the transferred side's telephone to receive the transfer, and it is possible to talk to the transferred side's telephone and the central office line simply by lifting the handset. In addition, even if the handset is put down after being placed on hold and then forgotten, the hold will be canceled due to the voltage drop between the office lines caused by the shearing when the subscriber is locked out at the exchange, and the phone will automatically return to its original state. return.

(Embodiment 1) FIG. 1 shows an automatic hold release device which is an embodiment of the present invention. SCR is a thyristor as an example of a semiconductor switching element with a self-holding function, C is a capacitor, R is a resistor that holds the central line, D is a reverse current blocking diode, and CNT is an anode of the thyristor SCR when the capacitor C is discharged. This is a control unit that controls the applied potential.

Next, this operation will be explained.

When a voltage is applied to the gate of the thyristor SCR due to the holding operation, the thyristor SCR becomes conductive, and the capacitor C is charged with the line-to-station voltage.
Further, the central office line is closed by a holding resistor R.

When attempting to release the hold, the voltage between the office line connection terminals drops due to the lifting of the handset of one of the telephones, causing the capacitor C to begin discharging to the control unit CNT. The control unit CNT detects the discharge and reduces or makes the voltage applied to the anode of the thyristor SCR zero. When the current flowing through the thyristor SCR becomes less than the holding current or becomes zero, the thyristor SCR becomes non-conductive. As a result, the pending state is released.
Note that many circuits are conceivable for the control unit CNT in the above embodiment.

According to such a configuration, it is possible to release the hold by a combination of the semiconductor switching element SCR and the capacitor C, but since the capacitor C is charged via the semiconductor switching element SCR which has a high resistance when conductive, the capacitor The charging voltage will be lower than the voltage between the station line connection terminals L ₁ and L ₂ , and the difference between the dropped voltage between the station line connection terminals at the time of re-response will be small, and therefore the hold release operation will not necessarily be stable. I made sure that this was not done. The embodiment described below solves this problem.

(Embodiment 2) FIG. 2 is a system diagram in which the control unit CNT is configured as an actual circuit to form a parent-child telephone device.

REC ₁ and REC ₂ are rectifiers, SCR is a thyristor which is an example of a semiconductor switching element with a self-holding function, C is a capacitor, Q ₁ , Q ₂ , Q ₃ are transistors, R ₁ , R ₂ , R ₃ , R ₄ , R ₅ , R ₆ , and R ₇ are resistors, SD is the sounder that sounds when a transfer call occurs, LED is the transfer indicator that lights up during a transfer call, and CK ₁ and CK ₂ are the contacts of the call switch used during transfer. , CK ₁ and CK ₂ are the contacts of the call switch used during transfer, S is the privacy circuit, SR is the privacy release circuit,
ZD is a Zener diode. TEL ₁ , TEL ₂ ,
TEL ₃ is a telephone. ADP ₁ , ADP ₂ , and ADP ₃ are additional devices connected to the telephones TEL ₁ , TEL ₂ , and TEL ₃ , respectively, and their contents are the same. Note that items indicating the same function are indicated by the same symbol.

Next, the operation will be explained.

Operation for making a call to the office line Now, when the handset of telephone TEL ₁ is raised to make a call to the office line, a switch contact (not shown) operates, and the following route is closed.

Office line connection terminal L ₁ - Rectifier REC ₁ - Secret circuit S -
Call switch contact CK ₁ - Rectifier REC ₁ - Telephone
TEL ₁ - Office line connection terminal L ₂ .

The above-mentioned loop makes the private communication circuit S conductive, and the office line communication circuit of the telephone TEL ₁ is closed, resulting in the office line capture state.

In this state, another telephone, for example TEL ₃ , attempts to acquire the central office line by raising the handset and activating the switch contact. However, at this time, the line voltage between the office line connection terminals L ₁ and L ₂ has been greatly reduced by the previously captured telephone TEL ₁ , so the Zener diode ZD does not conduct and the secret line circuit S is not conductive. Therefore, all telephones other than TEL ₁ are disconnected from the central office line.

Receiving operation When a bell signal arrives from the exchange side when a call is received on the central office line, the telephones TEL ₁ , TEL ₂ , and TEL ₃ are connected to the central office line connection terminal L ₁ - Rectifier REC ₁ - Secret circuit S -
Call switch contact CK ₁ - Rectifier REC ₁ - Telephone
TEL ₁ (TEL ₂ , TEL ₃ ) - A bell signal is applied through the route of the central office line connection terminal _L2 , and each telephone gives an audible indication of an incoming central line call. At this time, if you raise the handset on either telephone, the confidential communication circuit S of the telephone with the handset raised will be activated in the same way as in the case of making a call to the central office line described above.
conducts, but the secret circuit S of the telephone whose handset is not lifted up becomes non-conductive. The central office line is then routed to the telephone with the handset raised, and only this telephone can answer incoming central telephone calls.

Transfer Operation Next, an explanation will be given of an operation when transferring a call from telephone TEL ₁ to telephone TEL ₃ , as an example, during a call on a central office line.

In this case, when the call switch provided on the additional device ADP ₁ is operated, the call switch contact CK ₁
and _CK2 are driven to a state opposite to that shown in FIG. 2, and become conductive with the thyristor SCR activated through the following route.

Office line connection terminal L ₁ - Rectifier REC ₁ - Secret circuit S -
Contact CK ₁ - Gate of thyristor SCR - Resistor R ₅ -
Rectifier REC ₂ - Office line connection terminal L ₂ . Thyristor SCR
The station line caused by activation is held in the following loop.

Office line connection terminal L ₁ - Rectifier REC ₂ - Resistor R ₁ - Thyristor SCR - Resistor R ₅ - Rectifier REC ₂ - Office line connection terminal L ₂ .

In this way, in the present invention, the station line capture current flows through the circuit including the thyristor SCR, so there is no need to provide any other station line capture circuit, and therefore,
The configuration is simple and inexpensive.

Furthermore, due to the conduction of the thyristor SCR, the base current flows through the resistor _R6 to the transistor _Q1 , causing the transistor _Q1 to conduct. When the transistor _Q1 is turned on, the capacitor C is charged through the following route.

Station line connection terminal L ₁ - Rectifier REC ₂ - Diode D ₁
- Capacitor C - Transistor Q ₁ - Rectifier REC ₂
- Station line connection terminal L ₂ .

Thus, in this example, capacitor C is connected to diode _D1 , which has low resistance when conducting, and transistor
Since it is charged via _Q1 , its terminal voltage is approximately equal to the voltage between the station line connection terminals. In addition, the sounder SD of the additional device ADP ₁ sounds due to the operation of the call switch contact CK ₂ , and the other additional devices ADP ₂ ,
The sounder of ADP ₃ rings via the calling line L ₃ to notify that a call for transfer has occurred.

That is, the additional devices ADP ₂ and ADP ₃ are connected by the following loop formed between the office line connection terminals L ₁ and L ₂ .
Sounder SD is started.

Office line connection terminal L ₁ - (additional equipment ADP ₂ , ADP ₃ ) -
REC ₂ - Sounder SD - Calling line L ₃ - (ADP ₁ ) - Contact
CK ₂ − Diode D ₂ − Transistor Q ₁ − Rectifier
REC ₂ - Office line connection terminal L _Second , return the call switch CK (not shown) of the additional device ADP ₁ . However, since the thyristor SCR has a self-holding function, it continues to conduct and maintains the station line hold state. The transfer indicator LED of the additional device ADP ₁ is now lit. Furthermore, if the call switch is repeatedly operated for transfer, the transfer indicator LEDs of other additional devices will also light up via the following route.

Office line connection terminal L ₁ - (additional equipment ADP ₂ , ADP ₃ ) -
Rectifier REC ₂ - Transfer indicator LED - Control line L ₄ - (Additional device ADP ₁ ) - Contact CK ₂ - Diode D ₂ - Transistor Q ₁ - Rectifier REC ₂ - Station line connection terminal L ₂ Also, additional device ADP ₁ The privacy circuit S is rendered inoperative (non-conducting) by the privacy cancellation circuit SR via the following route.

Office line connection terminal L ₁ - Rectifier REC ₁ - Confidential release circuit
SR - Transistor Q ₁ - Rectifier REC ₂ - Office line connection terminal L ₂ , i.e. de-privacy circuit via the above route
When a current flows through SR, the potential of the line connected to the confidential communication circuit S changes, thereby making the confidential communication circuit non-conductive and canceling the confidential communication.

(b) In response to a transfer call, for example, when the handset of the telephone TEL ₃ is raised, the secret circuit S of the additional device ADP ₃ becomes operational (conductive). Therefore, the office line is also connected to the loop of telephone TEL ₃ through the following loop, so the voltage between the office line terminals decreases.

Office line connection terminal L ₁ - (Additional device ADP ₃ ) - Rectifier
REC ₁ - Confidential circuit S - Contact CK ₁ - Rectifier REC ₁ - Telephone TEL ₃ - Office line connection terminal L ₂ . Due to this voltage drop, the capacitor C of the additional device ADP ₁ that performed the transfer operation is discharged through the following route, and the transistor
Make _Q2 work.

Capacitor C (+) - Transistor Q ₂ (E-B)
- Resistor R ₂ - Resistor R ₄ - Capacitor C (-). Furthermore, the discharge current flows as a base current to the transistor Q ₃ through the following route due to the conduction of the activated transistor Q ₂ and operates the transistor Q ₃ .
Capacitor C (+) - Transistor Q ₂ (E-C)
- Resistor R ₃ - Transistor Q ₃ (B-E) - Capacitor C (-).

When transistor _Q3 operates, the local line current bypasses thyristor SCR through the following route, the current flowing through thyristor SCR becomes smaller than its holding current, and thyristor SCR becomes non-conductive.

Station line connection terminal L ₁ - Rectifier REC ₂ - Resistor R ₁ Transistor Q ₃ (C-E) - Transistor Q ₁ (C-E)
- Rectifier REC ₂ - Office line connection terminal L ₂ .

Transistor where thyristor SCR becomes non-conductive
_Q1 loses base current and becomes non-conducting, turning off the transfer indicator LED and turning off the privacy release circuit SR.
Control is performed to operate the confidential communication circuit S. Operation (continuity) of the secret circuit S of the additional device ADP ₁ on the transfer side
As a result, the telephone TEL ₁ on the transfer side is connected to the central office line again through the following loop.

Office line connection terminal L ₁ - (Additional device ADP ₁ ) - Rectifier
REC ₁ - Confidential circuit S - Contact CK ₁ - Rectifier REC ₁ - Telephone TEL ₁ - Office line connection terminal L ₂ .

Therefore, the telephone TEL ₁ and the telephone TEL ₃ are connected to the central office line, and the telephone TEL ₁ notifies the telephone TEL ₃ of transfer.

Once the handset of the transfer side telephone TEL ₁ is lowered, the secret circuit S becomes non-conductive, and even if the handset is raised again, the voltage between the central office line connection terminals has decreased significantly due to the telephone TEL ₃ , so the secret circuit S becomes disconnected. There is no continuity and the confidentiality of telephone TEL ₃ is maintained.

(c) Next, we will explain the case where the person making the transfer and the person receiving the transfer are the same person. The transfer operation was explained in (a) above, so the subsequent explanation will be given below.

If you hang up the handset after performing a transfer operation on the transfer side telephone TEL ₁ , the central office line will be held only in the holding loop shown below. Office line connection terminal L ₁ - Rectifier REC ₂ - Resistor R ₁ - Thyristor SCR - Resistor R ₅ - Rectifier REC ₂ - Office line connection terminal L ₂ .

Next, the person who performed the transfer operation moves to the transferred phone.
When the handset of TEL ₃ is raised, the holding loop of telephone TEL ₁ is broken as described in (b) above, and the central office line is connected only to the transferred telephone TEL ₃ in the following loop. Office line connection terminal L ₁ - (Additional device ADP ₃ ) - Rectifier REC ₁ - Secret communication circuit S - Contact CK ₁ - Rectifier REC ₁ -
Telephone TEL ₃ - Office line connection terminal L ₂ .

Therefore, it is possible for one person to change telephones and continue talking without having to perform any troublesome operations. Note that even if you put down the handset after performing a transfer operation and forget about it, the station line voltage will drop due to the interruption at the time of subscriber lockout on the exchange side, and the capacitor will discharge, causing the thyristor SCR to It becomes non-conductive. The hold will then be automatically released.

In addition, after being put on hold, either of the transferred telephones TEL ₂ ,
If the handset of TEL ₃ cannot be picked up, the hold switch will be canceled by momentarily turning off the switch of transfer telephone TEL ₁ , and telephone TEL ₁ will be connected to the central office line.

In the second embodiment, if only the telephone TEL ₁ is provided with the function of transferring, the automatic hold release device need only be provided in the additional device ADP ₁ .

In the second embodiment, the telephone and the additional device are separated, but there is no need to separate them, and the additional device may be incorporated into the telephone.

In the second embodiment, a system diagram of a parent-child telephone device is shown, but the present invention is not limited to this system diagram.

Embodiment 3 FIG. 3 shows another embodiment of the automatic hold release device. _Q4 is a transistor that becomes non-conductive when the hold is released.
Q ₅ is a transistor that detects the discharge of capacitor C, C ₂ is a DC blocking capacitor, and R ₈ and R ₉ are appropriately determined resistors.

Since the parent-child telephone device is the same as that in the second embodiment, only the automatic hold release device will be described below.

When the thyristor SCR is triggered by a pending operation, the thyristor SCR connects the station line connection terminal L ₁ - Transistor Q ₄ (E-B) - Resistor R ₈ - Thyristor SCR -
Conducting through the route of the station line connection terminal L ₂ , the capacitor C is connected to the station line connection terminal L ₁ - diode D - capacitor C - thyristor SCR - station line connection terminal L ₂
It is charged via the following route. Therefore, the central line is held in the next loop. Office line connection terminal L ₁ - Resistor R - Transistor Q ₄ (E-C) - Thyristor SCR - Office line connection terminal L ₂ .

Next, when the handset of any telephone is raised, the capacitor C starts discharging due to the voltage drop across the office line. The capacitance of capacitor C is the capacitor
Since it is much larger than C ₂ , the capacitor C
causes a discharge current to flow between the emitter and base of transistor _Q5 , making transistor _Q5 conductive. The conduction of transistor _Q5 short-circuits the emitter and base of transistor _Q4 , making transistor _Q4 non-conductive. Therefore, the thyristor SCR also becomes non-conductive and the suspension of this circuit is released.

(Effects) As explained above, the present invention creates a compact automatic hold release device using a semiconductor switching element and a capacitor having a self-holding function, and configures a parent-child phone device to communicate with a person who transfers a call. The recipients may be the same person. Also, to release the hold, you can simply lift the handset,
There is no longer any need to hold exchanges invalid. moreover,
Since the local line capture current during hold flows through the semiconductor switching element which is in a conductive state during hold, there is no need to separately flow the local line capture current, thus simplifying the circuit configuration and reducing costs. In addition, as in the second embodiment, charging of the capacitor for releasing hold is not performed through a semiconductor switching element, but is performed through a path with low impedance, so that the capacitor is charged almost to the station line voltage. As a result, the difference from the station line voltage that decreases when the hold is released can be made large, so that the hold can be released stably.

[Brief explanation of drawings]

FIG. 1 is a circuit diagram of an automatic hold release device which is an embodiment of the present invention, FIG. 2 is a system diagram of a parent-child telephone device,
FIG. 3 is a circuit diagram of an automatic hold release device according to another embodiment. SCR...Thyristor, C...Capacitor,
CNT...control unit, CK ₁ , CK ₂ ...call switch contacts, R, R ₁ ...resistance, REC ₁ , REC ₂ ...rectifier, Q ₁ , Q ₂ , Q ₃ , Q ₄ , Q ₅ ... ...transistor,
SD...Sounder, LEC...Telephone, ADP ₁ ,
ADP ₂ , ADP ₃ ...Additional device, S...Secret circuit,
SR...Secret release circuit.

Claims (1)

[Claims] 1. In a parent-child telephone device configured by connecting a plurality of telephones in parallel to a telephone line, at least one
a semiconductor switching element having a self-holding function connected between two telephone lines in a telephone or a device attached to the telephone; a capacitor that is charged by the voltage of the telephone line when the semiconductor switching element is electrically connected; When the line is put on hold, the semiconductor switching element having the self-holding function is triggered to conduct, and a hold loop is formed for the telephone line via the semiconductor switching element.At the same time, the capacitor is connected to the telephone line when the hold loop is closed. The capacitor's charge is discharged by the voltage drop that occurs between the telephone lines when the telephone itself or another telephone connected in parallel answers the telephone line again. A parent-child telephone device configured to automatically release the holding state of the telephone line by reducing the current flowing through the semiconductor switching element having the self-holding function to a value equal to or less than the holding current using a transistor that conducts. automatic hold release device. 2. In a parent-child telephone device configured by connecting multiple telephones in parallel to a telephone line, at least one
a semiconductor switching element having a self-holding function connected between two telephone lines in a telephone or a device attached to the telephone; a first transistor that becomes conductive when the switching element is conductive; and a first transistor that is conductive when the first transistor is conductive; a second transistor that detects discharge of the charge of the capacitor; and a third transistor that is made conductive by the second transistor, and the self-holding function is performed when the telephone line is put on hold. triggering a switching element having conduction, supplying a base current to the first transistor to conduct it due to the conduction of the switching element, and forming a holding loop for the telephone line by the conduction of the first transistor; A capacitor is charged with the voltage across the telephone line, and when the telephone itself or another telephone connected in parallel answers the line again, the capacitor discharges due to the voltage drop between the telephone lines, and the current generated by the discharge is transferred to the telephone line. supplying the base of the second transistor to the base of the second transistor, and making the third transistor conductive by the conduction of the second transistor;
The self-holding of the semiconductor switching element with the self-holding function is achieved by eliminating the potential difference between the anode and the cathode of the semiconductor switching element with the self-holding function during the self-holding due to conduction between the first transistor and the third transistor. 1. An automatic hold release device for a parent-child telephone device, characterized in that the hold state of a telephone line is automatically canceled by canceling the hold state of the telephone line and making the first transistor non-conductive.