Abstract: A temperature control system for a building or the like having a plurality of individually-controlled temperature zones wherein temperature variations from a set temperature generate actuating signals for valves, dampers or other regulating devices to vary temperatures in respective zones. The regulating devices are controlled by electrical-to-mechanical transducers which convert electrical actuating signals from a central controller to mechanical displacements at respective regulating devices. Each actuator has a piston assembly operated by working pressures which vary as a function of temperature in the zone being controlled. Pressure on the piston assembly is controlled from an expansion chamber containing an evaporatable-condensable refrigerant which is selectively heated and/or cooled by a semiconductor thermoelectric module.