| 摘要 |
A vehicle access transmitter and receiver pair which cooperate to implement a code transmission strategy which requires a minimum amount of energy thereby accomplishing maximum battery life while achieving operations secure from unauthorized access. The transmitter produces a string of start-and-stop pulse pairs which are each spaced in a timed interval so as to represent unique values. In operation the transmitter generates a sequence of four start-and-stop pulses with the duration of start-and-stop pulse pair proportional to the respective key code. The receiver detects the pulses and supplies them to a code comparison circuit. A lock code is stored and supplied to the code comparison circuit. During the reception time between each start-and-stop pulse in a pair, the demodulator counts up sequentially producing a vector sum of the lock code and the received code value. If the vector sum of all code valves stored and received equals zero, then a VALID signal is generated by the code comparison circuit permitting access to the vehicle via the selected path, i.e., Door, Trunk, etc.
|
