What parts make up an alarm system? Panel, sensors, siren

Alarm panel: the brain of the system

The panel is a metal or plastic box usually mounted inside a cupboard or on a wall out of sight. It reads the signals from the sensors, checks whether the system is armed and, if necessary, sets off the sounder and alerts you. The backup battery is usually inside this box too.

The first thing to look at when choosing a panel is the number of zones. A zone is each sensor or group of sensors the panel recognizes separately. If you want to connect eight sensors to a six-zone panel, you either combine two sensors in the same zone or buy an expansion card. With combined sensors, you cannot tell which one was triggered when the alarm goes off. If you are thinking of adding a room, storeroom or garden later, leave some spare zones.

Whether the panel keeps an event log also matters. The event log stores information such as who armed the system and when, and which sensor was triggered and when. Without this log, finding the cause of false alarms becomes much harder.

Sensors: door contact, motion and glass break

A magnetic contact has two parts. One is mounted on the frame, the other on the door or window sash. When the sash opens and the two parts move apart, the panel detects it. On doors and windows, it is the first line of defense because it warns before anyone gets inside.

A motion sensor is also known as a PIR. It detects the movement of body heat in the area and protects the inside of the room. If someone opens a window where there is no contact and climbs in, this is the sensor that catches them. If you have pets, you need to choose pet-immune models.

A glass break detector listens for the sound glass makes as it breaks. It is useful in shops with large display windows and on wide panes where fitting a contact is difficult. Besides these, extra devices such as curtain sensors, outdoor sensors and flood or smoke detectors can be connected to the same panel.

Sounder: indoor and outdoor

An indoor sounder disturbs the burglar inside and wakes the people sleeping at home. An outdoor sounder is mounted on the facade and warns the neighbors and people in the street. Most outdoor sounders have a strobe; it keeps flashing after the sound stops, showing which building the alarm went off in.

If the outdoor sounder comes with its own small battery, it keeps sounding for a while even if its cable is cut. In the Şanlıurfa summer, facade temperatures get very high. The housing and battery of a sounder mounted on a wall in direct sun wear out over time, so a spot under the eaves or in the shade is chosen where possible. The sounder also needs to be high enough to be out of easy reach.

How long the sounder sounds is set on the panel. A sounder that sounds too long disturbs the neighbors needlessly, while one that sounds too briefly goes quiet before catching anyone's attention. Discuss this duration during installation based on where you live. In an apartment, an indoor sounder is often enough; in a detached house or a shop, an outdoor sounder does the job.

Keypad, remote and app

The keypad is where you arm and disarm the system. It is usually mounted near the entrance door. Models with a display show which zone has been left open; you see the window you forgot to close before arming the system. Some keypads also work with a card or key fob, which makes things easier for older family members who find it hard to remember a code.

A remote control and a phone app do not replace the keypad; they complement it. When your phone is off or its battery is dead, the keypad still works. An entry delay of a few seconds is set between the entrance door and the keypad, so when you come in you have time to enter the code.

Expert note: Have the keypad mounted where it cannot be seen from outside, through a window or through a gap in the door. A keypad where you can be seen entering your code is a weak link, however good the rest of the system is.

Communication module and backup battery

If no one is home when the sounder goes off, no one may hear it. The communication module gets the alarm to you. A GSM module works like a mobile phone line: a SIM card is inserted, and it calls you or sends a message. An internet module connects to the modem and sends notifications to the phone app. Using both paths together means that if one is cut, the other keeps working.

The backup battery powers the panel, sensors and sounder when the power goes out. How long the battery lasts depends on the number of connected devices and the age of the battery. A battery loses capacity over the years, and the only way to find out is to test it. During maintenance, the battery should be tested under load.

How to read the parts list in a quote

When comparing two alarm quotes, look at the parts list before the total price. The items below are the points most often missing or vaguely written in quotes.

• The brand and model of the panel, and how many zones it supports.
• How many magnetic contacts and motion sensors there are, and which ones are pet-immune.
• Indoor or outdoor sounder, and whether the outdoor sounder has a battery and a strobe.
• Whether the keypad has a display.
• Communication path: GSM, internet or both.
• The capacity of the backup battery, and whether cabling, installation and programming labor are included.

Expert note: For wireless systems, have the quote state which battery type the sensors use. Some sensors use special batteries that are not available everywhere, and years later this becomes a small but annoying expense.

How many of each part do you need?

The layout of the home determines the numbers. A contact is considered for every door and window on the ground floor and every one opening onto a balcony. One motion sensor goes at each passage point such as the hallway and the living room; a burglar has to pass through these areas to move through the home. On upper floors, windows that cannot be reached from outside do not always need a contact.

During the on-site survey, Desa Bilişim identifies every point through which the building could be entered and prepares the parts list according to this plan. That way you know in advance where each sensor in the quote will be mounted.

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