JPH0218631Y2 - - Google Patents

Description

[Detailed description of the invention] This invention consists of a main device and a button telephone connected to the main device, and a secret telephone circuit for a button telephone device in which multiple telephone lines (hereinafter referred to as office lines) are used by the plurality of button telephones. The present invention relates to a confidential communication circuit that disconnects a telephone communication circuit network at a contact point of a relay to make the communication confidential.

Although many secret call circuits for pushbutton telephones have been proposed and implemented in the past, the present invention aims to reduce the number of parts as much as possible and to stabilize the operation. In other words, the main components are one relay, one transistor, and one control element with a self-retaining function (hereinafter referred to as SCR), which not only realizes the same confidentiality as before, but also reduces the connection cable between the main device and each button telephone. It is characterized by realizing prevention of malfunctions due to conductor resistance using an inexpensive circuit.

The present invention will be described in detail below with reference to the drawings.

Figure 1 shows an example of a conventional confidential communication circuit
No. 115906). The method of disconnecting the telephone communication circuit at the contact point of a relay uses a confidential circuit to determine whether the control line corresponding to the central office line is empty or busy.
A common method is to operate a privacy relay, disable a space/time privacy relay, and send out busy information. In addition, when determining whether the line is busy or idle, it is common to use a constant voltage diode or the like to ensure that malfunctions do not occur due to potential differences due to the line resistance of the control line.

In FIG. 1, reference numeral 3 indicates a part of the main device, 2 indicates a part of the key telephone, and 1 indicates a conventional example of a confidential circuit within the key telephone. The control lines 1H and 2H corresponding to the office lines 1 and 2 are connected to each telephone set in duplicate and housed in the main device 3, so that the state of the control lines can be monitored by the main device.

To answer or make a call to central line 1, press the central line selection button LK ₁ (not shown) on the button telephone side and raise the handset, and the contacts LK ⁰ ₁ , LK ¹ ₁ , and LK ² ₁ of LK ₁ will operate. Since the contact HS of the switch is closed, if the station line is empty, the following will occur: Earth - Contact HS - Terminal S ₁ - Resistor R ₅ - Diode
D ₄ - Constant voltage diode ZD - --- | | | -- Resistor R ₄ SCR (G-K) --- Diode D ₂ --- | | | --- Terminal S ₂ --- Contact LK ⁰ ₁ --- | ｜ ｜ --Terminal 1H -- Resistor R ₁₁ -- Control line -- (1H) Main device 3 Station line lamp BL ₁ -- Power supply E By _{the B} circuit, current flows between the gate G and cathode K of the SCR, making the SCR conductive. ,Hold. Therefore, the ground air at the contact point HS is sent to the control line 1H. this
The air passing through the SCR is sent to other key telephones as busy information. On the other hand, even if you press the station line selection button LK ₁ and raise the handset in order to interrupt the station line where busy information is being sent from another telephone, the SCR gate,
No current flows to the cathode and the SCR remains off. Therefore, in the interrupted button telephone: Earth - Contact HS - Terminal S ₁ - Diode D ₃ - Resistor
A current flows through the circuit of R ₃ , R ₂ - resistor R ₁ - terminal S ₃ - power supply E _B , and the potential difference across resistors R ₂ and R ₃ turns on transistors TR ₀ and TR ₁ , operating relay J. The telephone communication circuit network N is disconnected from the line by the contacts j ⁰ and j ¹ and the conversation becomes confidential.

In the circuit described above, the constant voltage diode ZD prevents the voltage drop in the power supply line and earth line due to the conductor resistance of the wiring cable between the main unit and the button telephone set, and prevents it from performing other functions, such as turning on the busy lamp or operating the call amplifier. This is a guarantee that the power supply may be large due to the fact that the power supply is used even when cutting. That is, the earth terminal S ₁ −
SCR - Diode D ₂ - Terminal S ₂ - Contact LK ⁰ ₁ - Terminal 1H - Even if earth air is sent to the control line in the control line (1H) circuit, it is not a complete earth potential and there is a potential difference in the above route. . Therefore, to ensure that the SCR does not become conductive due to this potential difference on the key telephone device that interrupted the call, and that the confidential communication is not lost, an appropriately selected constant voltage diode ZD is inserted.
Also, on the interrupted button telephone side, earth - contact HS - terminal S ₁ - resistor R ₅ - diode
D ₄ − Constant voltage diode ZD − Resistor R ₄ − Diode
The resistance values of ZD and R _{1 and the trigger current sensitivity of the SCR must be selected so that no current flows in the circuit of D 1 -} resistor R ₁ - terminal S ₃ - power supply E _B and the SCR becomes conductive. Therefore, the resistance value of _R1 is relatively high. Therefore, in order to drive the relay J, since the base current is extremely small, it is necessary to carry out Darlington amplification using the transistors TR ₀ and TR ₁ , which requires two transistors.

Figure 2 shows the constant voltage diode ZD shown in Figure 1.
An embodiment of the confidential communication circuit of the present invention, which aims to omit the circuit and consist of one transistor, is shown below. To answer or make a call to central line 1, press central line selection button LK ₁ on the button telephone and raise the handset.
Contacts LK ₀ ¹ , LK ¹ ₁ , LK ² ₁ , and LK ³ ₁ of LK 1 operate, and contact HS of the hook switch closes, so the _following changes occur: Earth - Contact HS - Contact LK ³ ₁ - Terminal S ₁ - Resistor R ₁ −
In the circuit of diode D ₁ - transistor TR ₀ (B-E) - terminal S ₃ - power supply E _B , base current flows through transistor TR ₀ , transistor TR ₀ becomes conductive, and relay J operates. If relay J operates, its contact j ³
By closing, Earth - Contact HS - Contact LK ³ ₁ - Terminal S ₁ - Resistor R ₃ - Contact j ³ --- | | | --Resistance R ₄ SCR(GK) --- | | | | ₃ - In the circuit of power supply E _B , gate current flows to SCR and SCR becomes conductive. If SCR conducts, resistance R ₁ − diode D ₁ −
The current in the transistor TR ₀ (B-E) disappears, and the base current to the transistor TR ₀ stops flowing, but on the other hand, the control line (1H) of the corresponding station line changes due to the operation of the contact j ² of the operating relay J. Determine whether it is busy or empty. If the empty state (1H) is not earth, the base current to the transistor TR ₀ will completely disappear, so the relay J will be restored. When relay J is restored, contact j ² is restored, and earth - contact HS - contact LK ³ ₁ - terminal S ₁ - contact j ² -
Terminal S ₂ - Contact LK ⁰ ₁ - Terminal 1H - Control line (1H) -
The circuit of the main device 3 sends out air to the control line (1H) to send busy information. If the control line (1H) is at earth potential, the busy lamp BL ₁ of the other duplex-connected key telephones and the own key telephone is lit through the resistor R ₁₁ to indicate that the telephone is busy. Therefore, if the central office line is empty, the one-carrier relay operates and then recovers, transmitting busy information and connecting the telephone communication network N through contacts j ⁰ and j ¹ to enable telephone communication on the central line. do.

In the above state, when you press the station line selection button LK ₁ on the other button telephone side to interrupt the same station line and raise the handset, the contacts of the station line selection button on that button telephone LK ⁰ ₁ , LK ¹ ₁ , LK ² ₁ , LK ³ ₁ and the contact HS are operated, so as mentioned above, the transistor TR ₀ is turned on and the relay J is operated, and the contact j ³ triggers the SCR and turns on the SCR.

On the other hand, when contact j ² operates, the control line (1
Since earth air is sent to H), earth air - control line (1H) - terminal 1H - contact LK ⁰ ₁ -
A base current is supplied to the transistor TR ₀ by the circuit of terminal S ₂ - contact j ² - resistor R ₂ - diode D ₂ - transistor TR ₀ (B-E) - terminal S ₃ - power supply E _B. Therefore, contact j ³ conducts SCR, and resistance R ₁
- Diode D ₁ - Transistor TR ₀ Even if the base current through the route of (B-E) is cut off, the transistor TR ₀ remains conductive. Therefore, relay J maintains its operation without being temporarily restored as if the control line were in an empty state. As a result of the above, contacts j ⁰ and j ¹ of relay J
As a result, the telephone communication network N is disconnected from the central office line 1, and the conversation becomes confidential. Note that the drawing mainly shows the circuit diagram for one button telephone of a telephone device equipped with two central office lines, but if the number of central office lines increases, the number of control lines and central office line selection buttons may be increased to account for the change. That's fine. Also, the power supply E _B is usually placed inside the main unit.

The operation of the confidential communication circuit according to the present invention has been explained above with reference to examples. However, if the confidential communication circuit according to the present invention is applied, the main components are one relay and one
The same purpose as conventional circuits can be achieved using an SCR and one transistor. In addition, even if a potential difference occurs in the power line due to wiring cables, etc., it has no bearing on the SCR trigger condition, and even if the air as busy information sent from the key telephone during a central line call is not completely electric, A stable secret communication circuit can be constructed without using a constant voltage diode or the like to guarantee a drop in power supply voltage such as ground level.

Therefore, compared to the conventional confidential telephone circuit, the present invention has a cost advantage by reducing the number of main parts, and is also effective in terms of stabilizing operation. It is a circuit.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram of a conventional key telephone device equipped with a secret call circuit. FIG. 2 is a circuit diagram of a key telephone device equipped with a secret call circuit, which is an embodiment of the present invention. 1... Confidential circuit, 2... Part of a button telephone,
3... Part of the main device.

Claims (1)

[Scope of Utility Model Registration Claim] In a button telephone device in which a main device and a plurality of button telephones are connected in multiple ways by control lines corresponding to telephone lines, each button telephone has one relay and one for driving the relay. It has two transistors and one control element with a self-holding function, and the power is turned on when the central line selection button of the button telephone is operated to answer or make a call to the telephone line, and the transistor is connected to the transistor from the power source. The relay is operated by supplying a base current of 1, and the operation of the first contact of the relay causes the control element having a self-holding function to conduct, thereby interrupting the first base current. However, when the telephone line to which a response or call is to be made is in an empty state, the relay is restored by cutting off the first base current of the transistor, and the restored second contact of the relay restarts the telephone line. and the telephone communication circuit network of the key telephone to cancel the privacy, and supply a power supply indicating a busy state to the control line corresponding to the telephone line which is in an empty state through the restored third contact of the relay. a relay which simultaneously cuts off the first base current of the transistor when a telephone line to which a response or a call is to be made is in a busy state, and operates from a control line corresponding to the telephone line which is in a busy state; supplies a second base current to the base of the transistor through a third contact of the transistor to maintain the relay in operation and connect the busy telephone line to the active second contact of the relay. A confidential communication circuit in a button telephone device, characterized in that the communication is kept confidential by cutting off the telephone communication circuit network of the button telephone.