A method and apparatus for detecting an input signal.

摘要

A low signal detection circuit (24) for use in an electronic tolling system which wakes up a receiver circuit associated with the tolling system based upon the type of signal received detects incoming RF signals and counts the rising and falling edges of the baseband signal and applies the counts to a threshold circuit (36) which will compare the number of counts to a predetermined value. If the number of counts falls within a predetermined range, then a signal present signal will be output from the wake-up circuit (24). A power management circuit (32) receives a clock signal from an oscillator (30) and provides a power signal which wakes up the detection circuitry for only a minimum predetermined period of time.