The direct-voltage intermediate circuit (14) has a positive potential connection (+VDC), a negative potential connection (-VDC), and a central point connection (NP).

The two direct voltage converter units (GW1, GW2) have a common input potential connection (Pe) and a common reference potential connection (Pb).

One potential terminal is assigned to a voltage supply (VDD) and the other potential terminal is assigned to an earth connection (VSS).

The antenna arrangement consists of a radiating element (5) that has an input connection (10) and a reference potential connection (15).

The phase conductor (Lu) is connected to the positive potential connection (+VDC) by means of a first diode (35') and to the negative potential connection (-VDC) by means of a second diode (36').

The reference potential connection (15) is connected to the reference potential (25) of a reference potential surface (30) by means of a first impedance (20, 35, 40).

The potential of the positive pole is high, and the potential of the negative pole is low.

The decoder gate has a number n+1 of inputs (IN1 - INn-1, INn, /INn) and at least two outputs (OUT1, OUT2) with a first (P1) and a second (P2) potential terminal.

The first reference plate (200) is connected to a reference potential terminal (42)of the sending/receiving unit (40) and the second reference plate (200) is connected to a reference potential terminal (32) of the antenna (30).

The control terminal voltage change portion (50) includes a switch (51) and a resistor (52) which are serially provided between the control terminal (10a) of the variable resistance value switch (10) and the reference potential terminal.

The first and the second parallel resonators (P11, P12) are commonly connected by a common connection GND terminal (23).

The direct-voltage intermediate circuit (14) has a positive potential connection (+VDC), a negative potential connection (-VDC), and a central point connection (NP).

Power supply potential is input to a power supply terminal, and ground potential is input to a ground terminal.

The first connection terminal (36) is connected to a first potential (UB), and the third connection terminal (40) is connected to a second potential.

The two direct voltage converter units (GW1, GW2) have a common input potential connection (Pe) and a common reference potential connection (Pb).