TRANSMISSION MESSAGE SIGNAL GENERATING METHOD AND CIRCUIT IN AUTOMOBILE TRACING DEVICE

摘要

The transmission method comprises the steps of generating message selection data according to the types of emergency situations of the vehicle tracker. A message signal is generated according to the message signal data. The message signal is shaped into in-phase and quadrature-phase component signals to make a uniform envelope. The frequency of the in-phase and the quadrature- phase signals are converted according to an oscillating frequency. The frequency converted signal is then amplified. A carrier frequency is filtered out of the amplified signal to transmit the filtered signal to the central control station. A signal indicative of a follow-up measure being taken from the station is received when the follow-up measure has been taken at the station.