Half the installation cabled and half by radio. And well.

DSC is a long-established intruder detection house, today inside Johnson Controls. Its best-known line for professional installation is PowerSeries Neo: a modular panel that grows with bus expanders and that takes radio detectors in the same system, mixed in with the cabled ones and treated the same. From the same group comes the IQ line, all-in-one panels with a touchscreen, aimed at small installations and at living in the app; which models of that line are available changes from country to country, and that is checked before it is offered.

You find it in offices, clinics, shops, medium-sized warehouses, branches and residents' associations. And above all in one particular scenario: the building already in use, with the suspended ceiling closed, the floor laid and nobody willing to open up walls. There a hybrid panel is not a concession, it is the sensible way of doing it.

The cabled part is the classic: the panel with its zones, a four-wire bus off which hang keypads and expanders spread through the building, zones supervised with an end-of-line resistor to tell alarm, tamper and cut apart, and independent partitions with their own arming, schedule and users.

The radio part is the one that deserves an explanation, because that is where this house has something of its own. The protocol is called PowerG and it is nothing like the alarm radio of fifteen years ago. It is two-way: the panel does not wait for the detector to speak, it asks, and it knows whether it is alive, with how much battery and with what signal quality. It hops frequency, which makes it far harder to knock out with a jammer. It is encrypted. And it shares out the time between devices in turns, so that two detectors do not tread on each other, which was the old failing of radio in installations with many points.

That shows in two things. The range: it is among the best at going through a real building, and that means fewer repeaters in an industrial unit with steel racking. And the autonomy: because it talks little and sleeps a lot, the batteries last years. How many depends on how the supervision is configured, which is an adjustment with a price —the more often the panel asks, the sooner you know a detector has died and the less the battery lasts— and which may be set by the grade the installation calls for. Outwards, network and mobile network communicators with both routes live at once and supervised.

And then there is what no brand fixes, which is most of it. A radio detector put where the signal reached instead of where the detection was needed. An infrared in the blast from the air conditioning, which fires when the machine starts and therefore at the same time every day. A microwave detector aimed at a plasterboard partition: the microwave goes through it and sees the forklift on the other side. A masking fault every morning at six, which is not a fault but a pallet parked in front of it. That is caught by reading the last few months of the log zone by zone and it is fixed by changing the position, the lens, the technology or the angle —sometimes half a metre is enough—, not by lowering the sensitivity. And the zone under building work is isolated on paper and with a date for coming back, because whatever is omitted «until they finish» stays omitted for two years.

The European standards split installations into security grades according to risk, and each grade asks for specific things: how each zone is supervised, how much autonomy you have to have with no mains, how tampering is detected, how often the transmission route is checked and, on radio, how often each device is supervised and how interference is detected. It is set by the activity, the insurance or a specification; the installer does not choose it. And two things quotations put together have to be kept apart: equipment certified for a grade is not an installation that meets that grade. What can be said of a hybrid line is that it lets you design zones with different demands inside the same system; what grade is handed over is signed by whoever hands it over, in writing and with a date.

The alarm receiving centre is a separate decision, with its own contract and its own regulations, and with one obligation that changes the design: the alert is verified before the police are called out. That is why verification by image turns thirty alerts a month into thirty ten-second dismissals.

It fits very well the building in use that has to be protected without building work: offices, clinics, shops, branches, units that have grown in pieces. It fits when you have to mix genuinely cabled zones —the perimeter, the entrances, whatever is more demanding— with radio where reaching with cable is absurd. And it fits where it is valued that the system knows the state of every device without anybody going to look at it.

It does not fit if the installation is so large and demanding that the sensible thing is a panel with an addressable bus and rings: forcing a hybrid to that size is paying in maintenance what you saved on purchase. Nor if the client wants nothing to do with batteries and there is a way of cabling. And the all-in-one line with a screen is designed for small installations that live in the app: where there are several areas with different schedules and somebody who is going to ask for traceability it falls short, and the place to discover that is not the third month.

The client runs the day-to-day without help: users and codes, who can arm which partition, part-arming, schedules, one-off isolation of a zone, and reading the log and the state of the devices. The app adds something that here gets used a lot: knowing whether it was left armed on the way out, arming remotely if somebody forgot, and seeing which battery is low without calling anyone. That is real management of the system, and it is worth teaching on handover day.

What needs the installer is the layer underneath: pairing a new device, changing the supervision or the times, touching the confirmation logic, adding expanders, redoing partitions, changing what is transmitted to the receiving centre and upgrading versions. And if the installation was handed over with a grade, any of those means the documentation has to be reviewed: the paperwork has to carry on describing what is there.

Battery replacement is decided on purpose: with twenty devices the client changes them if the type is written down for them and they are warned that opening the cover sets off the tamper; with two hundred it is a calendar in the contract, because the battery that does not get changed is a zone that does not protect. And the usual, handed over and charged for: training by role and documentation worth having — a drawing with every device, its battery type and its signal level at handover, partitions and schedules, and who receives which alert.