Patent ID: 7185825

Claim:
A programmable thermostat for controlling space conditioning equipment comprising: A) means coupling suitable power for energizing said thermostat from said space conditioning equipment to said thermostat; B) an interactive interface for a user to enter programming information into said thermostat; C) a temperature sensor for providing an electrical signal indicative of the temperature of a conditioned space in which the temperature sensor is situated; D) a processor, said processor including: 1) a central processing unit; 2) a first memory coupled to said central processing unit for storing program and data information; and 3) an input/output unit including: a) a sensor input coupled to said temperature sensor for receiving said electrical signal therefrom; and b) a control output coupled to the space conditioning equipment for issuing control signals thereto; 4) a real time clock; 5) a non-volatile random access memory; and 6) a control program stored in said first memory directing: a) said real time clock to periodically read its current time and date information into said non-volatile memory; and b) upon restart after a loss and then return of power from said space conditioning equipment, read the time and date information stored in said non-volatile memory into said real time clock.