FOR WATCHMEN — PHONE CALL

In connection with the aggravation of the criminogenic situation in the country is increasing the demand for security devices. In accordance with the laws of the market grows offer electronic guard for every taste (often with a predominance of the most sophisticated circuitry). Representatives of different companies vying to convince you to purchase state of the art microprocessor designs, the caller is automatically its owner to work or service in the attempts of the attackers to disable the security system and break into the safe house (a dacha, garage). Only here the prices “bite”. And where is the guarantee that replicated the electronic trickery you will not find criminal Kulibin?

Well, if you go the other way, which, by virtue of simplicity, it might be better advertised?

One extremely simple (and in some cases quite effective) technical solutions for protection of telephones of objects is what is called on the surface. Its essence is to use a phone call as an indirect source of information about the condition and integrity of door, window and other alarm sensors. However, for this they need to be connected to the telephone line according to a certain scheme without making disruptions in the functioning of the linear hardware and all of ATS as a whole.

As a chartered engineer, who gave the work in large telephone exchanges more than a year, with all responsibility assert that the implementation of all said above is possible and threatens to conflicts with ATS. The installation of the proposed security mini system does not require interference in telephones, does not load the telephone network DC. It requires only the train (a conductor working “on a break”) or a sensor with normally open contacts (e.g. reed switch) Yes condenser from a number of MB, KBG or K73 (capacity 1 µf, rated voltage 160 V).

The options are circuit diagrams of the simple but quite effective security mini system with loop sensor, working “on the cliff” (a), and a contact sensor or a reed switch (b) reacting closure

By the way, these capacitors long been used in telephony, and even specially installed in the phone Jack that when you turn off the subscriber’s apparatus line had the required capacitive load. That is the basis of the proposed security mini system has long been used by telephone networks. It only remains, without breaking anything, how to use it for custom solutions of security problems.

So while, say, at work, call home. And depending on the kind of sensor (loop “on open” or sensor with normally open contacts is selected during the installation of security mini-system by the owner) to get the answer — indirect information about the protected facility status: frequent busy signal or, conversely, a rare “free, no comments”. That is, the incoming signal of a telephone call is dropped (when connecting a capacitor parallel to the wire telephone network) as if it were raised up. Additional feature: with parallel phone you cannot dial the number for the set pulses are smoothed out by the capacitor. Than not protection, and of phone the pirates?

V. BESEDIN, Yu T m e n l