Security device with telephone line alarm. Encyclopedia of radio electronics and electrical engineering

Encyclopedia of radio electronics and electrical engineering / Security devices and object signaling

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It is known that not all citizens who decide to install an alarm in their apartment can afford to use the help of specialized security companies. The author of the proposed article has developed a device that allows you to acquire a security system without resorting to their services.

The described security device uses a chain of normally closed sensors connected in series. When any of them is opened, it automatically dials a predetermined telephone number an infinite number of times and gives specific sound signals. The subscriber on the other "end" of the wire, having understood the meaning of these signals, can return the device to standby mode by giving a command with a DTMF signal, and take care of eliminating the threat to the protected object. A significant drawback of such a device is the need to take special measures to protect the telephone line, since if an intruder cuts the line, it will be neutralized. But more on that at the end of the article.

The diagram of the device is shown in the figure. It is assembled on three microcircuits: DD1 - control part, DD3 - universal dialer with last number memory, DD2 - DTMF dialing decoder for remote control. All functions of the device are implemented in hardware, without the use of microcontrollers, which makes it accessible for repeating by radio amateurs of average qualification.

(click to enlarge)

Two triggers are assembled on the DD1 chip, conditionally named "Mode Trigger" (elements DD1.1 and DD1.2) and "Alarm Trigger" (DD1.4 and DD1,5). Their states are shown in the table.

After the first supply voltage (or after pressing the SB1 "Reset" button), a low level occurs at the output of the DD1.1 element. At the same time, the input of element DD1.4 is also low and the "Alarm Trigger" does not respond to any manipulations with the sensors. The output DD1.4 is high, the transistor VT2 is open, and VT1 is closed. The device is in the Disabled state.

Leaving the apartment, the owner presses the button SB2 "Protection" and holds it for 2 ... 3 s. Current flows through the VD3HL1R5SA1 - SAn circuit. If any sensor is open, the HL1 LED will not light up. In addition, the condition of the GB1 battery is monitored. If it is discharged, the HL1 LED flashes brightly and immediately goes out. A high level through the diode VD2 is input to the element DD1.2 and puts the "Mode Trigger" into a state where its output (DD1.1) is high. However, until the capacitor C3 is discharged through the resistor R3, the input of the element DD1.4 "Alarm Trigger" will be low and the owner can leave the apartment. With the ratings of the elements C3 and R3 indicated in the diagram, this time is about one minute.

If any of the sensors SA1 - SAn is open, a high level will appear at the input of element DD1.3. The pulse generated by the VD6R6C4 circuit will switch the "Alarm trigger". At its output (DD1.4) there will be a low level, the transistor VT2 will close, and VT1 will open. Through transistor VT1, LED HL2, transistor VT3, resistor R25, a current of about 30 mA will flow from the telephone line. The VD6R6 circuit will prevent the trigger from switching back if the open sensor closes again.

The high level received at pin 1 of the DD3 chip starts dialing. The set pulses come from pin 9 of the DD3 chip. To form a line break when dialing, this pin (open drain) goes low. At pin 8 (also an open drain), a low level is present during the dialing of the entire number, so the input of the DD1.6 element will be low, and the output will be high. At the end of dialing, the signals at the listed points will change to the opposite ones. A low level will occur at pin 16 of the DD3 chip, which activates the "Redial" function (repeat the last dialed number).

A feature of the UM91215A chip is that it includes the "Flash" function as part of the "Redial" function. Thus, the DD3 chip will dial the number previously entered into its memory an infinite number of times, making the necessary disconnection from the line between dialing attempts.

Clock pulses on the DD3 chip come from the DD2 chip generator through the capacitor C9. Such an inclusion, in addition to saving a quartz resonator, also introduced a "zest". The fact is that the DD2 chip receives power through the R21VD20 circuit only when the VT1 transistor is open. As soon as DD3 generates the "Flash" command. VT1 will close, the capacitor C12 will be discharged (the DD2 chip consumes about 10 mA) and the master oscillator DD2 will stop working. The DD3 chip will remain without clock pulses, and the "Flash" time will increase from 600 ms to 20...30 s.

This effect can be useful if you want to set up an alarm to be sent to a pager using a DTMF channel. To turn off the device when receiving a signal, dial the number to which it is connected (you need a telephone set with the ability to switch to tone dialing), wait for the next dialing attempt and dial the number "2". If you do not need to transmit an alarm signal to a pager, then you should connect a quartz resonator to the DD3 chip in the same way as to DD2, or use a larger capacitor C12.

Upon returning home, the landlord switches the device to the "Disabled" mode by pressing the "Reset" button SB1.

To write a phone number to the DD3 chip, you need to connect a standard 3x4 keyboard [1,2] to it. You can do this using the connector, connecting only for the time of programming.

The programming procedure is as follows. Press and release the SB2 button. Wait for capacitor C3 to discharge. Press and hold the SB3 "Programming" button. In this case, the "Alarm Trigger" will go into the "Alarm" state, the device will take the telephone line (the HL2 LED will light up), but the "Redial" function will not be activated, since the capacitor C10 is shunted through the VD11 diode. Denote by the letter "P" button SB4 "Pause". Press buttons: "P", "X", "X", "X", "X", "X", "X", "*", "P", "1", "P", "1" , "P", "1" ... "P", "1", "P", "1" (28 characters in total, including pauses, but no more!). Here "ХХХХХХ" is the phone number where the device will call. Release the SB3 button and briefly press SB1. LED HL2 should go out.

The "*" button puts the DD3 chip into tone dialing mode. Button SB4 ("P", "Pause") introduces a pause of 3 seconds into the dialed number. The tone dialing signals of the number "1" will be those very "specific" alarms. If access to the city network is made through the prefix ("8", "9" or others), then after dialing it, enter 1 - 2 pauses.

When a tone signal corresponding to the number "2" arrives at the input of the DD5 microcircuit through the C9R2 circuit, a high level occurs at its output D1, which switches the device to the "security" mode (namely, "Protection", and not "Disabled", since the capacitors C1 and C2 do not have time to discharge). The pulse at the output D1 of the DD2 chip is short, since with its arrival the device is immediately disconnected from the line. At the end of the impulse, the "Mode Trigger" switches to the "Protection" state.

The VD12 diode is installed if the PBX does not accept the pulse dialing. Then you need to connect the output of the resistor R14, right according to the scheme, to the common wire, and the DD3 chip will be switched to the tone dialing mode. The signal from pin 8 DD3 through the VD12 diode will block the output stages of the DD2 chip during dialing. The remote shutdown signal will pass to the DD2 output only after the end of the set of the entire sequence programmed in DD3, but before the activation of the "Flash" function. This time may need to be increased by using a larger capacitor C10. Diode VD12 is also required when transmitting an alarm signal to a pager.

The R17VD15VD13 circuit provides the device with power in the Disabled and Armed modes. Resistor R17 is selected like this. so that a current of the order of 1 μA flows through the battery GB100 (three "AA" cells in the direction of its charging. The rating indicated in the diagram provides such a current at a voltage in the telephone line of 60 V. Resistor R21 is also selected according to the same criterion. but already in the "Alarm" mode ".

The C13R22VT3 cascade is needed to transmit tone signals to the line. Resistor R24 ​​- load internal amplifier chip DD3. Diodes VD4 and VD5 were introduced during the testing process - after a thunderstorm, the DD1 microcircuit failed (it broke through the input of the DD1.3 element).

Chip DD2 can be replaced by KR1008VZH18, and DD3 - by chips of the UM91215, UM91214 or KR1008VZH27 series. The same microcircuits with the letter B and KR1008VZH27 have 18 pins. Insert them into the socket so that pins 9 and 10 remain free. Chips with the letter C also have 18 pins, but they need to leave pins 1 and 18 free. Chips with the letter D, which have 20 pins, have pins 1, 10, 11, 20 free [2]. Instead of transistor VT1, it is permissible to use the KP1014KT1B key.

About line protection. Ideally, if the distribution cabinet is located on the back side of the wall of your apartment. Drill a hole in the wall like this. so that you can stick the wire directly into the interfloor channel. If this is not possible, you will have to lay the wires under the plaster. In any case, it is advisable not to remove the external wires, but to include them in the sensor circuit from the side of the apartment, while closing them together in a shield and masking the end. It is possible, by agreement with the neighbors, to connect the device to their line through the wall between the apartments.

Literature

1. Kielyuk A.I. Handbook on the device and repair of telephone sets of foreign and domestic production, - M .: Biblio, 1997.
2. Integrated circuits. Microcircuits for telephony and means of communication. - Dodeka Publishing House, 1999.

Author: I. Shiryaev, Yekaterinburg; Publication: cxem.net

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