According to the invention a rail vehicle wheel sensor assembly (ZCK) is provided that comprises a rail vehicle wheel detection system (UWK) and a two-wire interface in the form of a current loop, by means of which the wheel detection system (UWK) is connected to an external device (SO). The wheel sensor assembly (ZCK) is characterised in that it comprises a wheel detection configuration system (UKDK) connected to the wheel detection system (UWK), an authorisation and configuration system (UA) capable of storing at least one secret (SK), used for secure communication with the external device (SO) and for forwarding configuration commands to the wheel detection configuration system (UKDK) connected thereto, a communication converter system (UM) used for the signal conversion, a wheel sensor supply voltage conversion system (UKU), a voltage summation and voltage-to-sensor-output-current conversion system (UKUI), an output signal permission system (UZSW) and a power supply system (UZ).

According to the invention a rail vehicle wheel detection device (DWK) comprising two or more such wheel sensor assemblies is further provided.

A rail contact element for drop off detection is disclosed, wherein the rail contact element is mountable to a rail and includes a spring element, a main body which holds the spring element and an optical fiber. The spring element is in a tension state or in a relax state depending on a mounting state of the rail contact element. The optical fiber includes an outlet surface for emitting a light beam and the rail contact element further includes a reflector element. The spring element, the reflector element and the optical fiber are arranged so that the influence of the reflector element on the light beam is different in the tension state than in the relax state.