Expansion Box

A wired system is the most robust option: the detectors have no batteries to replace, they are immune to radio interference and jamming, and with end-of-line (EOL) resistors the panel also detects a cut or shorted cable, so it is the first choice for new buildings or renovations where cable can be run in conduit. A wireless system installs quickly and without damage in finished homes and offices, and detectors are easy to move, but each detector's battery typically has to be replaced every 2 to 5 years, the radio range must be tested on site, and the system should be two-way and supervised so that a lost detector or jamming is reported. For many projects the best answer is a hybrid panel: wired detectors wherever cabling is easy and wireless ones for points that are hard to reach with cable. KDT's KB-M2 panel is hybrid, with 6 wired zones on board, expandable to 192, and support for up to 100 two-way 868 MHz wireless devices.

Every burglar alarm system has a few main parts: the control panel, the brain of the system, which monitors the zones and makes the decisions; a keypad, remote control or mobile app for arming and disarming; detectors such as PIR motion detectors, door and window magnetic contacts, glass-break sensors and shock sensors; indoor and outdoor sirens, usually with a strobe light; and a communicator (dialer) that reports events over a landline, the mobile network or the internet. A power supply with a backup battery keeps all of these parts working during a power cut. Each detector is connected, by cable or by radio, to a zone, that is, a numbered input on the panel, and the panel decides from the zone type and the arming state whether a change on that zone counts as an alarm.

Design in layers: first the perimeter, that is, a magnetic contact on every door, window and balcony door that can be reached; then the interior, that is, PIR detectors on the routes an intruder has to take, such as the hallway and the living room; and finally point protection for a safe or a valuables cabinet. List every possible way in, including balconies, roof hatches, skylights and walls shared with a neighbouring unit, and give each detector its own zone so you know exactly which point was triggered. As a typical example, a 100 to 120 m² apartment needs a magnetic contact on the entrance door, 3 more on balcony doors and reachable windows, 3 PIRs and a smoke detector, plus a keypad by the entrance and an indoor siren: that is 8 zones, and with about 25% spare for later additions, 8 × 1.25 = 10, so choose a panel with at least 10 zones.

Install the keypad inside the protected area near the main entrance, on the entry route, so it can be reached within the entry delay, and where it cannot be seen from outside through glass. Install the control panel somewhere else, out of sight, for example in a closet or a plant room, inside the coverage of a detector and close to power and the network, so that an intruder cannot find and smash it during the entry delay. Mount the outdoor siren as high as possible on a wall that can be seen from the street, typically 3 m or more, so it cannot be reached without a ladder, and put the indoor siren where it cannot quickly be reached and silenced, for example high on a hallway wall. If the panel uses the mobile network, check the signal strength at that exact spot before the final installation.

An instant zone raises the alarm immediately when the system is armed and is used for windows and points that are not on the entry route. A delay zone, usually the main entrance door, starts the entry delay so the user can reach the keypad, and a follower zone, such as the PIR in the hallway between the door and the keypad, is normally instant unless the entry delay has already started. A 24-hour zone is active even when the system is disarmed and is used for tamper circuits, safes and technical sensors such as water leak detectors; the panic zone is also 24-hour and can be set to sound the siren or to be silent (only sending messages). A fire zone for smoke detectors is always active too and is signalled with a different siren pattern and report, so that it is not mistaken for a burglary.