The effectiveness of car alarms largely depends on where the sensors and the main unit are located. The better they are disguised, the more difficulty attackers will experience when trying to steal a car.
The main alarm unit should be located in a place where, on the one hand, it will hardly be affected by heat from the engine, and on the other hand, it will be difficult to detect. It can be hidden inside one of the chairs or its back, so that it does not interfere with sitting in this chair. Also, this unit can be located in the space behind the rear speakers. If it is thin enough, you can even place it under the headliner - the main thing is that it does not bulge out. If you place it in the traditional way - in the trunk or in the engine compartment, you will have to ensure its invisibility, and in the second case - also heat resistance. To a fairly small block, for example, you can attach a nameplate from a relay, and to a large one - from an audio amplifier. Of course, the alarm wiring will have to be carefully disguised, and next to it you can, if you wish, lead several fake, unconnected wires. A block equipped with a communication channel with a remote control key fob, as well as a GSM channel, should be placed in a place where it will not be shielded. massive metal parts. If this is not possible for reasons of stealth, you will have to use an external antenna. The radio antenna is not suitable - it is not hidden, and it is designed for a completely different range. The hidden flexible antenna of the unit (or two antennas, if it is equipped with a GSM module) can be hidden under the casing or dashboard as close as possible to the device itself. The location of the sensors should be chosen so that they react to the impact regardless of which side it is turns out. Microwave and ultrasonic detectors can be installed on any of the walls of the cabin, but they must be deployed in such a way that they react to movement at any point in its space. This will have to be verified empirically. The optimal location of the vibration sensor can be found by lightly tapping on the body from different sides - a properly positioned device should operate in all cases Microswitches that respond to opening doors, engine compartment lids and trunk lids should be placed inside fixed body parts adjacent to doors and covers … If you put them in the doors and covers themselves, the lead wires will be frayed sooner or later. Secrets, that is, switches, without which it is impossible to start the engine, can be placed in the most unexpected places in the cabin. Such a switch can even fit into the dashboard among many others of the same type. Better yet, disguise it using a reed switch. When setting up an alarm, do not forget that it should not become a source of danger. Exposure of wire insulation, threatening them with short circuit and fire, should be completely excluded. Their breaks should also be excluded, since a sudden cessation of engine operation while driving can lead to an accident.
