PTB Presence

Why a sensor rather than a report

An owner who isn't on site knows the business only through what people choose to tell them. The hotel register shows twelve rooms let; the till takes payment for nine. The warehouse guard insists the door was opened only for the morning delivery. The monthly report arrives clean, coherent, and thoroughly unverifiable.

The problem isn't dishonesty — most teams are honest. The problem is that a human report has nothing to be compared against. There is no second source to check it with, so there is no way to tell a mistake from a fraud, or either of them from a genuinely quiet night.

PTB Presence supplies that second source. A measured, timestamped reading that depends on nobody's account: the room was occupied or it was not. What you do next — cross-checking footfall against takings, explaining an energy bill, settling a dispute — stays your decision. The sensor doesn't judge, it records.

What the sensor measures, and what it cannot see

Presence detection uses radar, not a camera. The unit senses that a body is in the room and how far away it is; it produces no image, records no sound, and cannot identify anyone. That limitation is deliberate: it makes the device installable in a hotel room or an office without raising the question of consent to video surveillance.

Each unit also reports the room's temperature, humidity and air quality — volatile organic compounds, equivalent carbon dioxide, air quality index. Each of those has its own use: a room at 34 °C explains a complaint, sustained high humidity foretells damage to furniture, air degrading in a classroom is fixed by opening a window.

On top of that come a fire alert and a tamper alert. The first is sent without waiting for the next scheduled reading; the second reports that someone tried to open the device, which is information in itself.

How the installation works with no cabling and no socket

The sensors don't talk to Wi-Fi. They reach a single coordinator on site over LoRa on the 868 MHz band — a radio designed to cross a building's internal walls on very little power. Only that coordinator needs a socket and an internet connection; the sensors go wherever they are useful.

This is what makes the battery life possible. Between two readings a sensor cuts power to its own probes and drops into deep sleep, waking only to answer the coordinator. The device spends most of its life switched off, and runs for several months on its battery.

An internet outage doesn't interrupt measurement. The coordinator holds the last hundred readings in memory and uploads them when the link returns: the gap fills itself in, with no hole in the history and no intervention.

What you see, and when

The dashboard opens in a browser, on a phone or a computer, and installs to the home screen like an app. It shows the current state of every room, occupancy history over several months, and the conditions measured in each space.

It was built for a Cameroonian network, which is to say for a network that drops. The app keeps the last known situation in local storage: opened offline, it shows that data instead of a blank page, and states plainly how old it is. A write attempted with no network fails openly rather than disappearing in silence.

Alerts — fire, tampering, thresholds crossed — reach the phone as they happen. The monthly report sums up the period and serves as evidence when a discussion starts.

What setting it up involves

Reckon on one sensor per room to be monitored, and one coordinator per site. The coordinator is configured from a phone over Bluetooth: you give it the local Wi-Fi and the customer identifier, and it starts polling the sensors. There is no cabling to run, no drilling, and no work on the electrical installation.

We fit the hardware and check the range on site — a concrete wall doesn't behave like a plasterboard one, and that is established by trying rather than by calculating. Alert thresholds and user accounts are then configured from the dashboard, without us.