Architecture

 SENSORS                 ROOM COMPUTER            LOCAL SERVER                     SCREENS
 radar, oximeter,   ──►  one per room       ──►   message broker (MQTT)      ──►  nurse station
 thermometer,            (Raspberry Pi):          rules, baselines, alerts         nurses' phones
 bed pad, mic,           adapters per model,      escalation and paging            control room
 call bells              sound -> scores          journal (PostgreSQL)

• Sensors never talk to the server directly. They publish small JSON messages to a message broker over MQTT, one contract for every kind of sensor. A new sensor model needs one adapter, written once.
• The room computer is a small computer per room (a Raspberry Pi in production). It reads the room’s sensors, analyses sound locally and sends only scores, never recordings. In the demo, a simulator plays every room computer.
• The server decides: which devices are approved, which resident a reading belongs to, whether a rule fires, and the life of every alert. Everything it decides is written to a journal and replayed when it starts, so it survives a crash or a restart.
• The screens get the whole ward when they connect and every change after that, live. A screen that loses the connection says so.

What runs where in the prototype

Part	Technology
Message broker	Mosquitto (MQTT), QoS 1
Server	Kotlin and Ktor, one application
Journal	PostgreSQL, append-only
Nurse station and phone	Compose Multiplatform: the same code on the desktop and Android
Simulated ward, laptop microphone	Python

Everything runs inside the building, on its own network. Nothing goes to the cloud.