Abstract: An interrogator (Interrog) is additionally provided with a logic circuit (ActCommProt-ImplLCI) for implementing an active communication protocol and with a receiving second antenna (AI2) provided for an active communication. Said antenna is connected through an active receiver (AMActRecI) for receiving amplitude-modulated signals to said logic circuit (ActCommProtlmplLCI). A transmitting and receiving first antenna (AT1) in each transponder (Transp) is connected through an active receiver (AM-ActRecT) for receiving amplitude-modulated signals to a logic circuit (ActCommProt-ImplLCT) for implementing the active communication protocol, an output signal of which logic circuit is conducted through an active transmitter (AMActTransmT) for transmitting amplitude-modulated signals to a transmitting second antenna (AT2) for active communication. The transponder (Transp) is provided with a power supply circuit (SupplC).

Abstract: Output terminals (o1, o2) of a differentially excited transmitting circuit (TC) are connected through matching capacitors (MC1, MC2) to connecting terminals of the oscillatory circuit antenna (OCA) on the other side said connection terminals are directly connected to input terminals of a receiving circuit (RC). Each of the input terminals (i1, i2) of the receiving circuit (RC) is connected to an earthing terminal (m) of the integrated transceiver circuit (TRC) through a corresponding undervoltage-protection diode (UPD1, UPD2) determining a lower potential value of a received signal and a corresponding overvoltage-protection diode (OPD1, OPD2) determining an allowed upper potential value of the received signal exceeding said lower potential value by the highest possible voltage still allowable by the integrated transceiver circuit (TRC).