Patent ID: 7061985

Claim:
A modulation/demodulation device capable of operating according to a plurality of modulation types each using a different carrier frequency and comprising: a microprocessor for providing transmit digital information; a modulator for modulating, according to a given modulation type from among the plurality of modulation types, a transmit signal at a given carrier frequency based upon a signal of a predetermined duration representative of the transmit digital information; a sending/receiving device coupled to said modulator; and a demodulator coupled to said sending/receiving device and demodulating a received signal by determining a given type of modulation and given carrier frequency for the received signal, and analyzing the received signal based upon the given type of modulation to detect whether the received signal has the predetermined duration and supplying received digital information from the received signal to said microprocessor; said demodulator comprising: a plurality of bandpass filters each centered on a respective one of the carrier frequencies and filtering the received signal, a respective gain controllable operational amplifier coupled to each of said bandpass filters and providing an output, at least one comparator for comparing the output from each operational amplifier with a reference signal and providing a respective state signal for each output, and an encoding circuit for encoding the state signals to determine a modulation type of the received signal.