Security system has transponder with HF transmitter and further transmitter for data transmission to base station and/or to read/write device, e.g. with LF or acoustic carrier frequency

摘要

The system has a base station (10) and at least one transponder (T1-T5) that conduct a data dialogue between them, whereby the base station sends data to the transponder on a LF carrier in the LF range and the transponder sends data back to the base station on an HF carrier. The transponder has a further transmitter for data transmission to the base station and/or to a read/write device using an LF electromagnetic carrier frequency, an acoustic carrier frequency in the ultrasonic range or an optical carrier frequency in the infrared range, whereby the base station and transponder transmit at different LF frequencies. Independent claims are also included for a transponder and for a receiver.