Patent ID: 7961083

Claim:
A system comprising: a sensor to provide a signal corresponding to a status of an apparatus; a satellite receiver to detect the signal from the sensor and to provide a signal indicating the status of the apparatus via a signal line; a digital control circuit to receive the signal via the signal line and to supply power to the signal line, said digital control circuit to generate an indication signal to activate a device in response to receipt of the signal, the digital control circuit comprising: a signal line converter circuit to determine the signal line voltage and to generate a signal corresponding to a voltage level when the voltage level of the signal line is within a first predetermined voltage range; and a digital to analog converter circuit to set the voltage level of the power supplied to the signal line and to generate a voltage level within the second predetermined range, the first and second predetermined voltage ranges have maximum and minimum potentials with respect to ground; a synchronization circuit to generate a periodic sync pulse on the signal line for transmission to the satellite receiver; and a reference voltage generation circuit to simultaneously adjust the maximum and minimum potentials of the first and the second predetermined voltage ranges during the generation of the periodic sync pulse.