This alarm does not need to organize a separate line. The grid is a great way to replace it, at the same time remaining and power source. This is particularly useful in garages, in gardening companies, warehouses, etc. in Short, wherever there is mains. The communication range of the protected object receiver “alarming” high frequency (HF) signal within a large building or to 1 — 2 km from the garden plot, warehouse, garage, basement, i.e. in the area of one of the step-down substation (the corresponding phase of the mains).
We offer burglar alarm system consists of two devices: the transmitter (transmitters — the number of protected objects) and the receiver (the radio).
The RF signal (from 150 to 2500 kHz, is selected for each transmitter, but outside the frequencies of broadcast stations serving the same area), the modulated low frequency (LF), is transmitted through network wires and into the receiver. There it is amplified using the detector and decoder is allocated low-frequency component of an “alarm” signal. The result is relay, including an audible alarm.
The sending device (Fig. 1) comprises: a master oscillator (/T1), the modulator (/T2 /TK), a subcarrier generator (transistors (/T5 /T6), output (N”4) and a signal Converter security loop (on relay K1, diode VD6, the reed switches SF1 – SFN).
Schematic diagram of the receptor (Fig. 3) includes: a cascade RF amplifier (VT1, VT2), the detector (diode VD1), power LF (VТЗ-VТ5), the decoder transistor VТ6, an audible warning device (ВF1. VD8, /T7/T8)- the Number of decoders is set by the number of protected objects. After all, to distinguish the creatures from one another, each transmitter must have its frequency modulation. On this specific frequency is configured suitable for big business (in the diagram for simplicity shows only one) decoder.
Fig. 1. A circuit diagram of a transmission device
Fig. 1. A circuit diagram of a transmitting device.
Fig. 2. Circuit Board transmitting device
Fig. 2. Circuit Board of the transmitting device:
1 — transmitter unit, 2 — subcarrier generator, 3 — relay box security train, 4 — rectifier and stabilizer of the power supply.

Fig. 3. A circuit diagram of a receptor
Fig. 3. A circuit diagram of a receiving device.
Fig. 4. Circuit Board receptor
Fig. 4. Circuit Board receptor:
I — a receiver unit. 2-decoder, 3 – signal devices, 4 — rectifier and stabilizer of the power supply.

And transmitting and receiving device is powered from the mains And according to standard scheme using a step-down transformer. the rectifier and stabilizer. As the “siloviki” T1 here will fit any low-power, whose primary winding is designed to operate in the network (50Hz, 220V) into the secondary (of transformer T1 in the transmitting device, two such windings: II and III) 12-volt voltage.
“Disturbing” RF signal is received through one of the phases (“A”, “b”, “C”) to the receiver through a transformer T2. The latter in each winding 30 — 50 turns of wire PEL with a diameter of 0.3…0.5 mm, the core is a ferrite ring To 13x5x5. The capacitors C15, C16, C17 — 47 000 pF. Operating voltage to which they are to be calculated is in the range of 400…450 V.
Alarm transmitter outputs to the corresponding phase of the network also with the help of a transformer made on ferrite core a little more envelope — To 17x8x5. Both windings contain the here for 30 — 50 turns of wire of PEV in diameter of 0.4-0.5 mm. and, as the winding of the transformer T2 of the receiver, they should be separated from each other, good insulation (varnished cloth or PTFE tape).
High-frequency coil generator (transmitter) and RF amplifier (receiver) must be tuned to the same frequency. It is best to get them ready. For example, amplifiers of intermediate frequency transistor receivers.
But the LF coil decoder (L2) will have to make their own. It is wound on a ferrite (with permeability of 400 or 600НН) ring К17х8х5 and has (depending on the modulation frequency) 400…600 turns of wire PALCO diameter of 0.08…0.1 mm.
For stable operation of the alarm system we recommend the following frequency modulation (sub-carrier): 1700 Hz 2300 Hz, 3100 Hz, 3600 Hz, 4300 Hz, 5700 Hz. Setting on a particular frequency is produced by selecting not only the number of turns of the coil, but also the value of capacitor C7. Well, if the number of protected objects is not within the set of frequencies that will have the encryption and decryption of the RF signal to implement digital circuits. As is usually the case in other radio Amateur designs (“modelist-Konstruktor” No. 3.8 in 1994; # 4 and # 5 in 1995).
But back to our development. More precisely, to the signal Converter of the security loop. It contains electromagnetic relay K1, diode VD7, VD8, reed switches SF1 — SFN, a capacitor C15 and a current limiting resistor R20. The power relay is supplied from the winding III of the transformer T1.
Due to the geographically remote diode VD8 Converter react sensitively both on the break and short circuit — a situation introduced by cyber criminals. In both cases, the relay, releasing the anchor, a closed circuit of secondary winding II of the transformer T1. Then turn on the transmitter and on the corresponding phase will stressant RF signal (alarm).
The adjustment of the device begin with the transmitter settings. The first thing to achieve excitation of the main generator (L_1, /T1). The resulting high frequency oscillations can be detected either by the oscilloscope or RF voltmeter, or S-meter (indicator field).
Then excite low-frequency oscillations in the generator subcarrier (VТ5, VТб). It is not excluded that it will have to change the value of resistor R8. And make sure the oscillation can again with an oscilloscope or headphones.
Generator subcarrier (frequency modulation) can be adjusted individually: “your” decoder. This is achieved by selection of the values of the capacitors C10 C12…. Well, more accurate adjustment is performed by the resistor R14.
Indicated on the diagram the values of the capacitors and resis tori correspond to the subcarrier frequency of 2300 Hz. Remember that. Acceptable for the perception of sound signaling device (/T7 /T8) is selected, adjusting properly the resistor R19.
Final debugging of the receiver and transmitter are produced together. To do this, both devices included in the network. When properly configured (the subcarrier generator with the appropriate decoder) relay K1 of the receiver. Immediately “cut” signal, the device begins to buzz alarmingly speaker ВF1. If not, then connect the headphones via a 0.1 UF capacitor to the collector of transistor /T5 (see Fig. 1) and “take control” frequency modulation. If necessary, carry out adjustment.
You may need and aligning the receiver (high-frequency transmitter). Make it slightly turning the coil core of L1 amplifier of the RF signal (Fig. 3).
In fact, the sensitivity of our receptor sufficient — 2… 3 mV. To further increase is not necessary, as this can threaten the false positives of all schemes as a whole.
And a few more tips. To avoid any misunderstandings, it is advisable to install it in the enclosure thoroughly to make sure all the nodes on the dummy “makeshift”. For mounting blocks is recommended to use tabs of aluminum of 1.5 mm glass fiber (Fig. 2 and 4). And pads, solder parts to produce manufacturable method of mechanical cutting of the conductive layer. Electrical connections it is better to perform installation insulated wire type MGTF.
As part of the receptor can be adapted to any industrial radio with LW and MW bands. The output signal of the decoder in this embodiment is carried out from the volume control and basic speaker turned off (otpaivat).
This development is designed for a wide range of Amateur radio and does not claim for ideality. Of course, there are opportunities for improvement. It would wish. And work… He will be rewarded handsomely.
A. PARTIN, Ekaterinburg

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