Telephone operated heating, ventilating and/or air conditioning

Claim 1

Apparatus for selecting the temperature of a space in a building having an HVAC, from a standard telephone located outside of the building remotely from the building by means of dual tone multiple frequency (DTMF) signals transmitted over common carrier telephone lines, consisting essentially of: telephone connection means, including a ring detector, an answering circuit and a hook switch, for connection directly to common carrier telephone lines and operative in response to a telephone call directed thereto for answering said call; a tone decoder connected to said telephone connection means, responsive to DTMF signals received thereat for providing a first selected one of a plurality of command signals indicative of a command for a first temperature in response to a first combination of said DTMF signals and for providing a second selected one of said plurality of command signals indicative of a command for a second temperature in response to a second combination of said DTMF signals; a toggle system including a bistable device operable in either one of two stable states in response to an input signal provided thereto to assume the opposite one of said stable states, said toggle system providing a switching signal in response to said first selected signal concurrently with said bistable device being in a first one of said stable states and in response to said second selected signal concurrently with said bistable device being in a second one of said stable states, said switching signal being provided as an input signal to said bistable device; a bistable switch having a first conductive path enabled and a second conductive path disabled when said bistable switch is in a first one of two stable switch states and having said first conductive path disabled and said second conductive path enabled when said bistable switch is in a second one of said two stable switch states, said bistable switch switching from either of said two stable switch states to the other of said two stable switch states in response to an input signal provided thereto; a first thermostatic switch for connection through said first conductive path to the HVAC to cause said HVAC to operate at a first temperature set point, and a second thermostatic switch for connection through said second conductive path to the HVAC to cause said HVAC to operate at a second temperature set point; and means for communicating said switching signal to said bistable switch as an input signal thereto, whereby in response to DTMF signals indicative of a command for said first temperature said bistable switch will remain in or assume said first bistable switch state and in response to DTMF signals indicative of a command for said second temperature said bistable switch will remain in or assume said second bistable switch state, thereby to select the temperature set point for the HVAC.