Grumpy_Mike:
PWM is not a communication systemYou can do that if you construct it correctly. How far apart are these relays going to be?
i was going to create my own data bus system using pwm. the first 10 bits of data would have been addressing and the next 6 bits would have been the data passed to said address. maybe I'm not explaining my system to you in a way you are used to.
there need only be one relay for each location and each relay could be anywhere from two feet to 200 feet apart. although for the most part it will stay around 30 ft.