@qwertz1 Heartbeat support: the sensor can send a "heartbeat" message to the controller to let it know it's alive. The heartbeat message does not update values. Not all controllers can interpret the message. Ack: when you enable ack in a message the receiving node "acknowledges" the message by returning it. It is a way to make sure that the message arrived at it's destination. Some controllers can resend and/or report. This is used mostly for actuators (lights/ motors) to be it is switched on/off. OTA (over the air) means you can update the firmware (sketch) on the MySensors node without wiring it to the computer. Request: the controller supports "requesting" values. i.e. a node/sensor can request a last known value from the controller (or other node). Typical usage is to request a last know switch state from the controller after a node/ sensor powers up. Another usage ( at least for me) is requesting all kinds of information from the controller for remote display (V_TEXT). I hope it clears the sky for you..:sparkles: