> Usually it's just acting as a simple relay (on-off switch) so there's two physical wires. Vaillant has a proportional signal as well, and that thing in my ol

> Usually it's just acting as a simple relay (on-off switch) so there's two physical wires. Vaillant has a proportional signal as well, and that thing in my old home was 30 years old... [1] [1] https://www.mikrocontroller.net/topic/126250?page=single https://www.mikrocontroller.net/topic/126250?page=single