I am trying to understand how thermostats electrically modulate the compressor speed in a variable speed system.
My Radiothermostat sends 24V signal through the YELLOW wire to fire up the compressor of my single speed compressor and the 24V GRN for the blower. The YELLOW wire is binary (on / off) signal: on the other hand a variable speed compressor requires a non-binary signaling scheme, such as PWM so that more than one message can be signaled.
Does the a second controller somehow receive the YEL 24V signal and modulate the compressor speed in a variable speed system?
