Conventional fire alarm systems, supplied and installed in Lebanon.
The building is divided into zones, and each zone is one monitored circuit back to the panel. It is cheap to install, cheap to keep running, and there is very little in it to go wrong. It is also the right answer far more often than anyone selling addressable will tell you.
What a conventional system is.
A conventional system divides the building into zones and gives each zone one circuit. Every detector and call point in that zone sits on that circuit, and the panel watches the circuit as a single electrical thing. When something operates, the panel lights the zone. It does not know which device did it, and it was never built to. A zone is drawn small enough for that not to matter: normally one floor and one fire compartment, so a person walking in can find the operated device in under a minute.
At the far end of every zone circuit sits an end-of-line resistor, and the panel measures the current flowing through it. Around the expected current means the circuit is healthy and nothing has operated. A short means a device has operated: a detector switching on, or a call point's glass broken. Much lower current or none at all means the cable is open, and the panel calls that a fault rather than a fire. That one resistor is what turns a plain pair of wires into a supervised circuit, and it is why a conventional zone missing its resistor is not a working zone.
What a complete conventional system consists of.
Every part below does a job. Leave one out and the system will not behave the way the design says it should.
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Conventional control panel
Monitors each zone circuit, indicates the zone in alarm, drives the sounders and holds the charger and batteries.
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Zone circuits
One radial pair per zone, run out from the panel to the last device on that zone and terminated there.
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Conventional optical detectors
The general-purpose detector, on a base wired into its zone circuit.
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Heat detectors
Fixed-temperature or rate-of-rise, for kitchens, plant rooms and car parks where a smoke detector would false alarm.
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Detector bases
The device is a head in a base. The wiring stays in the base, so a head can be swapped without touching the circuit.
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Manual call points
Break-glass at every exit and on every escape route. Operating one shorts the zone and puts the panel into alarm at once.
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End-of-line resistors
One at the far end of every circuit. It is what lets the panel tell healthy from operated from broken.
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Remote indicator lamps
Repeats a detector's own lamp somewhere visible, for detectors above ceilings, in ducts and in rooms that stay locked.
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Sounder circuits
Their own monitored radial pairs, so a cut sounder cable shows as a fault before it matters.
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Sounders and strobes
Sized and sited so the alarm is heard everywhere in the building, and seen where it will not be heard.
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Panel relay outputs
Volt-free contacts for air handling shutdown, door holders, dampers and onward signalling.
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Power supply and standby batteries
Sized by calculation from the real standby and alarm load, so the system rides out a mains failure.
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Zone chart at the panel
A plan on the wall beside the panel showing what each zone covers. Without one, nobody standing at the panel can turn zone three into somewhere to go.
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Fire-resistant cabling
Rated to keep the circuit alive while the building is burning.
The numbers.
| Standard | NFPA 72, National Fire Alarm and Signaling Code |
|---|---|
| Circuit | One radial detection circuit per zone, back to the panel |
| Panel sizes | Commonly 2, 4 and 8 zones, extended by repeat or expansion panels |
| Resolution | The zone. Zones are drawn small enough to be searched quickly |
| Line monitoring | End-of-line resistor on every circuit, typically between 3.3 kΩ and 10 kΩ depending on the panel |
| Devices per zone | Set by the panel's zone current budget, commonly around 20 to 30 detectors |
| Detection | Conventional optical smoke detectors, and fixed-temperature or rate-of-rise heat detectors |
| Notification | Separate sounder circuits, also end-of-line monitored, or two-wire operation with the sounders on the detection circuit |
| Outputs | Panel relays for plant shutdown, door holders, dampers and onward signalling |
| Secondary power | 24 hours in standby followed by 5 minutes in alarm |
| Approvals | UL-listed or EN 54-certified components |
The buildings this suits.
Shops and showrooms
One trading floor, a stock room and an office. Three or four zones covers it properly.
Small offices
A single floor or a single tenancy, where a person in alarm is never more than a short walk from the device.
Workshops and light industrial units
One open space, heat detection over the work, and a system that survives dust and knocks.
Warehouse units
A single unit on a few zones, where the cost of running a loop around the building buys nothing.
Restaurants and cafés
Heat detection in the kitchen, optical in the dining room, and a wet-chemical hood system alongside.
Small residential buildings
A handful of floors and a common stair, where the zone is already the flat.
Extensions to an existing system
A new area added to a building that already runs conventional, matched to what is on the wall.
Built to NFPA 72, from listed components.
We design to NFPA 72 and build from components that are UL-listed or certified to EN 54. Detection coverage comes out of the ceiling heights and the compartments rather than out of a device count, standby batteries are sized by calculation from the real standby and alarm load, and the whole system is programmed to a written cause-and-effect matrix before anyone tests anything.
Commissioning proves it: every device operated, every zone or address confirmed against its label, sounder audibility checked through the building, and each line of the cause-and-effect tested in turn. What is handed over is the as-built drawings, the zone plan or address schedule, the cause-and-effect and the commissioning record, with a log book left at the panel. Those documents are what an insurer, an inspector or the next maintainer will ask for, and a system that cannot produce them cannot be shown to have been designed for the building it is sitting in.
What people ask about conventional systems.
What does a complete conventional fire alarm system consist of?
A conventional control panel, one radial zone circuit per zone, conventional optical smoke detectors and heat detectors on their bases, break-glass manual call points, an end-of-line resistor terminating every circuit, remote indicator lamps for detectors that cannot be seen, monitored sounder circuits, sounders and strobes, panel relay outputs for plant, a power supply with standby batteries sized by calculation, a zone chart mounted at the panel, and fire-resistant cabling.
What is an end-of-line resistor for?
It is what makes the circuit supervised. The panel pushes a small current through the zone and reads what comes back through the resistor at the far end. Normal current means healthy. A short means a device has operated. An open circuit means the cable is broken, and the panel raises that as a fault rather than sitting there looking fine while half the zone is disconnected. Values vary by panel, typically somewhere between 3.3 kΩ and 10 kΩ, and fitting the wrong one makes the panel misread the circuit.
How many detectors can go on one zone?
It is limited by the panel's current budget for a zone, commonly around 20 to 30 detectors. But that number is almost never the real constraint. What decides a zone is how quickly someone can search it: normally one floor and one fire compartment, and small enough that the person who walks in on a zone indication finds the operated device quickly.
Can a conventional system tell me which detector went off?
No, and that is the defining limit. The panel shows the zone. The detector that operated has its own indicator lamp lit, so you find it by walking the zone. That is exactly why a zone is drawn small, and why remote indicator lamps are fitted for detectors above ceilings, inside ducts or in rooms that stay locked.
Is a conventional system worse than addressable?
It is less capable, not worse. On a single-floor shop, a workshop or a small unit, a properly designed conventional system with a correct zone plan detects fire just as early, alerts just as loudly and costs a good deal less to install and to keep. It stops being the right answer when the building gets big enough that a zone is no longer quickly searchable, or when the system has to drive lifts, dampers and phased evacuation.
Can I add to an existing conventional system?
Usually. A new device goes on an existing zone if that zone has the capacity and still covers a sensible area, or the panel gets a new zone if there is a spare. Where the panel is full, an expansion panel or a change of panel is the honest answer rather than overloading a circuit. What we check first is whether the existing zone plan still describes the building, because extensions are where zone plans quietly go out of date.
What is the difference between two-wire and four-wire?
Four-wire runs the detection zones and the sounder circuits as separate pairs, which is the usual arrangement. Two-wire puts the sounders on the detection circuit itself, so the whole zone is one pair. That saves cable and lets the sounders be operated zone by zone. Two-wire needs a panel and devices built for it; the two cannot be mixed on one circuit.
How much does a conventional fire alarm system cost in Lebanon?
It comes down to the number of zones, the number of devices and how hard the building is to run cable through. An occupied building with finished ceilings costs more to wire than a shell. For a small unit it is still one of the least expensive pieces of life-safety equipment you will buy. Tell us the size of the building and how it is laid out and we will price it from a real zone plan.
How often does it need testing and servicing?
A call point or detector is operated at every visit on a rotating schedule so the whole system is proved over the cycle, every zone is put into alarm and the sounders proved audible, the end-of-line monitoring is checked by breaking a circuit deliberately, and the batteries are load tested. The zone chart is checked against the building, because a zone chart that no longer matches the layout is worse than none.
Related data sheets.
Send us the floor plans. We will design the system around them.
How many floors, what is on each one, and how the building is used at night. That is enough for us to come out, walk it, and put a real zone plan or device schedule behind the price.