In a tall building you do not evacuate everything. You evacuate in order.

The panel is the cabinet that asks every detector and every call point several times a second and decides what happens. What sets this family apart is that inside that same cabinet there is also the part that speaks: the amplifiers and the evacuation messages are not a separate system bought from somebody else and joined on with a couple of contacts.

The consequence is that the audio can be handled by zone and by channel: an evacuation message on the storey where the fire is, an alert message on the one above and the one below, and silence or information on the rest. That is what you need in a tall building, where getting everybody out at once fills the stairs exactly where the fire brigade has to come up.

You come across it in tall office buildings, hotels, hospitals, airports, university campuses and large public buildings. In general, where the evacuation is phased and where there is a fire brigade position in the lobby from which somebody is going to have to speak.

The cabinet is a structure of modules: the processor, the loop cards, the outputs and the audio amplifiers, each thing in its place and everything powered and supervised by the same system. Growing means adding modules; and several panels are joined on a network so that a building with several towers or a campus is seen from one place while having one panel per part.

The elements with their own address hang off the loops. In this family the detector does a good part of the work of deciding: it measures, interprets and sends a conclusion already made, as well as reporting how dirty it is getting so that the inspection goes to the points that call for it. With isolators spread out, a short circuit eats one section and not the storey.

On technology, the usual criterion: optical in offices, corridors, rooms and suspended ceilings; heat in kitchens, car parks and plant rooms; multi-criteria where sensitivity is needed in an environment that is not clean; flame outdoors and in tall industrial units; aspirating detection when the ceiling is very high or you have to find out very early, as in a server room.

And what decides whether the system is the one on the paper: the power supply. Batteries calculated with the real consumption, and with the amplifiers counted talking and not at rest. In a tall building you also have to decide what hangs off the generator, and that is discussed with maintenance instead of assumed.

The good part is that the detector is not a switch: it reports that it is getting dirty before it starts giving false alerts, so the inspection can be targeted and you know which corner of the building makes detectors dirty — which is usually the symptom of something else, a filter, a door that does not close, building work next door.

What that does not fix is the wrong technology. An optical detector at the air outlet of a kitchen, in a changing room with steam or on a loading bay where forklifts come in is going to go off until somebody disables it, and a disabled detector is still drawn on the plan. There you change technology, and that is design and not adjustment.

And there is a fault peculiar to systems with voice that no detector test shows up: that the message is not understood. A corridor with an echo, a hard ceiling, an open-plan storey with little absorption, loudspeakers badly shared out, and the result is a noise you cannot get any instruction from. It is checked by listening in the worst places and not in the lobby.

It fits where the evacuation has to be phased and in words: tall buildings, hotels, hospitals, terminals. It fits where there is a position from which somebody is going to direct the evacuation live, and where supervised audio —the system knowing if a loudspeaker or an amplifier has stopped being there— genuinely matters.

It does not fit an industrial unit with one loop and one sounder, nor a two-storey building where everybody gets out through the same door in a minute. There the audio is a cost that changes nothing, and there are simpler panels that do that job well.

Ours is the electrical and the electronic: the detection design, the control panel, the loops, the elements, the evacuation audio with its loudspeakers, the interlocks with lifts, air conditioning, smoke doors and access control, the commissioning and the maintenance.

The water, no. Sprinklers, fire hose reels, dry risers, pump sets and tanks are another line of work, with another licence and other trades, and in a tall building they are always there: we say it up front so the budget counts on both companies from the start. Of the gas fire suppression in a technical room we do the electronic part —detection, delay, warnings, release, abort and interlocks— and not the cylinder bank or its pipework.

Your people have to be able to silence, reset after checking, read the history and understand a fault alert. And in a system with phased evacuation, it has to be decided beforehand who gives the order to go from alerting one storey to evacuating the building, on what criterion and what gets said in the meantime. That is rehearsed; it is not improvised at three in the morning with the microphone in your hand.

Temporarily disabling a zone also belongs to your people, because it happens every week in a building with work going on inside. It is taught with a written rule and a record of who disables and who puts it back: the zone left out on a Friday afternoon is one of the most repeated holes there is.

What does not belong to your people: adding or moving elements, touching the programming, changing the messages and the sensitivities, updating the panel. That lives in a company licensed to maintain the installation, with its schedule and its signed file, and it is not a rule we have made up. What you can demand is the handover: drawings of what is there, one-page procedures and separate training for whoever operates and whoever maintains.