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Devices: sensors & actuators

Everything physically connected to the bus is a device. Devices fall into a few clear roles. Knowing the roles makes the device list on a project readable at a glance.

The three roles​

Sensors — they send​

A sensor detects something and posts a telegram. It never switches a load itself. Examples:

  • Push-buttons / switches (the most common "sensor" — a button is a sensor that detects a finger).
  • Presence and motion detectors.
  • Temperature, brightness, CO₂, humidity sensors.
  • Weather stations (wind, rain, sun).
  • Binary inputs (turn a conventional contact into a KNX sender).

Actuators — they act​

An actuator receives telegrams and drives a physical load. It is where the bus meets the building's power. Examples:

  • Switch actuators — relays that switch lighting/sockets.
  • Dimming actuators — vary lighting level (or a DALI gateway).
  • Blind/shutter actuators — drive motors up/down.
  • Heating actuators — drive valve outputs (often as slow PWM).

Actuators are multi-channel: one device might have 8, 16, or 24 channels. A channel is the unit you actually link group addresses to — "actuator 1.1.20, channel 3" is one switchable circuit.

System devices — they enable​

These do not sense or act; they make the network work:

  • Power supplies (one per line — the bus's energy).
  • Couplers (line/area/backbone — the topology joints, with filtering).
  • IP interfaces / IP routers (the door to KNX-IP and to the tool — see below).
  • Logic / visualisation modules, gateways (DALI, Modbus, SMI, EnOcean…).

The flow, end to end​

Note the dotted status path: a good installation has actuators report their actual state back to a status group address, so visualisations and KNX Clarity-style records reflect reality rather than "what was last commanded".

Transmission media revisited​

The same role exists across media — a KNX-RF push-button is still a sensor, a KNX-IP actuator is still an actuator. Media are bridged by couplers/gateways, and the whole thing remains one logical system addressed by group addresses.

What the catalog adds​

A bare ETS export gives you a device's manufacturer, order number, and application — but not a datasheet, a product photo, or its documentation. KNX Clarity's Catalog matches each parsed device against a curated product library so the device record carries the human context (what it is, what it looks like, where the manual is) — useful when a technician meets unfamiliar hardware on site.

Why KNX Clarity groups by room, not by role

ETS thinks in topology (lines) and function (group addresses). People servicing a building think "the actuator for the kitchen blinds". KNX Clarity's Rooms & devices view re-projects the same devices into the building structure so a non-engineer can find the right one.