The device (1) detects whether a safety belt lock switch is open or closed and whether a driver is belted in or not, whereby a magnetic switch (6) is arranged in the lock to detect its state. The belt lock switch has a circuit board (2) for connection to a base plate of the belt lock with conducting tracks (5), whereby the magnetic switch is electrically contacted by the tracks and a state signal can be output via an electrical connection with the tracks.
