This is Marklin 7555 Reed Switch
This is Marklin 7555 Reed Switch Schaltkontakt. The reed switch is for use at a suitable point with K Track or C Track. The reed switch triggers a pulse of current when a locomotive or car with a magnet mounted on the underside passes over it. The connections to the reed switch are potential-free. The reed switch has a maximum current capacity of 2 amps. Length 38 mm / 1-1/2.