I like those relays. Is that 3 different switched outputs? One thing I always liked about european wall switches is that they give you more room for components. I would like to use a similar type of relay for my in-wall switches, but with the way US single gang wall boxes are, there is a pretty narrow space constraint. I might be able to fit it if I did away with the thermal fuse, but I don't want to give up tat bit of added safety just for that.

What I didn't quite figure out was how it operates independently as a regular light switch. What I find most interesting is that this is 8 years old. There have been some incredible advances in the IoT world in that time. I was about to do a similar thing which morphed into an ESP-12F then added a touch screen. I call it the Universal Light Switch Imagine this: All the switches are identical. Any switch can easily be configured to control up to five devices ... and then changed, on-the-fly, to control a different set of devices. My design is part of a system that would require a controller (eg. Home Assistant), an MQTT broker, and receiving modules in the devices being switched. It's WiFI which assumes an access point. The DIY ULS is under $20 and the off-the-shelf receiving modules are under $10. (About the cost of a non-networked dimmer switch) If one doesn't have the controller and MQTT broker, they can run on an old (5 years?) computer (which is cheaper than an old RasberryPi). This project is a good one! OSD