Thermostat responsive to inputs from external devices

A system for controlling the operation of a heat pump and auxiliary heating system, comprising:

• a controller for a heat pump having a compressor that is configured to transmit signals indicating that the compressor is inoperable;
• an auxiliary heating system having a furnace control;
• and
• a thermostat connected via one or more wires to the controller for the heat pump and connected via one or more wires to the furnace control, for controlling the operation of the heat pump and the auxiliary heating system, wherein the thermostat is configured to respond to input signals from the controller indicating that the compressor of the heat pump is inoperable by discontinuing operation of the heat pump and requesting operation of the auxiliary heating system to initiate auxiliary heating operation, regardless of the outside ambient temperature
• further comprising a two-wire network that the controller for the heat pump and thermostat are connected to, wherein the controller for the heat pump is configured to transmit signals at a fixed time period after the last transmission, which fixed time period is unique to the controller for the heat pump, and the thermostat is configured to transmit signals at a fixed time period after the last transmission that is unique to the thermostat.