Power supply of a detection unit

A power supply device (1) for supplying power to an acquisition unit (2) disposed on a rail vehicle for monitoring operating units (3) of the rail vehicle and for monitoring a route of the rail vehicle, the rail vehicle having at least one conductor (4) and the power supply device (1) being configured for generating a supply voltage of the acquisition unit (2) from a voltage applied to the conductor (4), wherein a current collector (7) of the rail vehicle comprises the conductor (4), and wherein transmission electronics (5) and a bypass conductor (6) connectable in an electrically conductive manner to the acquisition unit (2) via the transmission electronics (5) are provided and the transmission electronics (5) is switched between the bypass conductor (6) and the acquisition unit (2) and the bypass conductor (6) is connected in an electrically conductive manner to the conductor (4) of the current collector (7), by means of two fastening interfaces (8), a potential difference being present between the fastening interfaces (8) and the bypass conductor (6) being designed in such a manner that the bypass conductor (6) generates an output voltage which is lower than the potential difference at the conductor (4) of the current collector (7) between the fastening interfaces (8), the transmission electronics (5) being designed in such a manner that the transmission electronics (5) generates the supply voltage of the acquisition unit (25) from the output voltage of the bypass conductor (6).