Abstract: Communication between the various elements of HVAC systems is effected by means of low-cost, low-power, narrow-band AM SAW-stabilized transmitters 21, 27, 39, 86 and receivers 18, 28, 47, 89. A residential embodiment (FIG. 1) transmits temperature information from each room of the house to a master control 24, which is used to control the HVAC demand and to control the damper in the corresponding room. In a first commercial building embodiment (FIGS. 2 and 3), thermostat/transceiver 61-66 assemblies transmit not only demand and control information from the corresponding thermostat 78 (with switches), but relay information transmitted from other thermostat/transceiver assemblies, whereby messages are retransmitted from one floor to the next to overcome the high attenuation of commercial building construction in reaching rooftop HVAC systems 71-76. In a second commercial building embodiment (FIG.

Abstract: A linear magnetostrictive actuator with feedback compensation including a force train that has at least one magnetostrictive element, an excitation component disposed on or within the actuator, a feedback apparatus whose output signal is proportional to the magnetic induction within the magnetostrictive element, and actuator control circuitry for providing the difference signal resultant between the feedback output signal and the external signal, such that positional displacement error is compensated by closed loop operation of the actuator.