Patent ID: 8160184

Claim:
A method comprising: receiving an amplitude-modulated time signal from a transmitter, the time signal comprising a plurality of markers representing time information, the amplitude-modulation of the time signal comprising modulation of an amplitude of a carrier of the time signal with a plurality of pulses, each pulse of the plurality of pulses corresponding to a respective marker and having a pulse width corresponding at least to a first pre-determined time duration representing a first binary value of the respective marker or a second pre-determined time duration representing a second binary value of the respective marker; demodulating the amplitude-modulated time signal to provide an analog signal; digitizing the demodulated analog signal by comparing the demodulated analog signal with one or more reference levels of a comparator; extracting time information from the digitized demodulated time signal; determining a characteristic value of one or more measured time durations of one or more first or second binary values of respective markers in the digitized demodulated time signal; comparing the characteristic value with the first or second pre-determined time duration; and adjusting one or more of the reference levels of the comparator based on the comparison of the characteristic value with the first or second pre-determined time duration.