Magnetic operated float switches for lateral mounting operate according to the principle of the communicating vessel. This reference vessel (4) contains a magnet-operated float switch. This basically consists of a slip pipe (5) with a mounted float (6). There are one or more reed contacts in this slip pipe. These have been adjusted to the value of the preset switching points stated in the order. The switching points cannot be adjusted. The float changes its height proportionally to the level of the medium. The magnetic field of the permanent magnet built into the float activates the reed contact on reaching the switching point.