| 摘要 |
An external indicator for use in proximity to an on-board unit or transpond er for an electronic toll collection (ETC) system. The external indicator sense s RF transmissions from the on-board unit and/or roadside readers of the E TC system and produces sensory outputs when transmissions are detected. The external indicator receives RF signals, demodulates them, and analyses the demodulated RF signals to determine if it has received a roadside reader trigger signal and/or a transponder response signal. A sensory indicator, such as a visual, auditory, or kinetic device, alerts an occupant of a vehic le to the detected RF transmissions and, accordingly, to the likely occurrence of an ETC transaction.
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