Reed sensors, in their hermetically sealed capsules, can switch as low as zero volts on up to 1000 volts with the same sensor and no added circuitry. Hall sensors in a magnetic field put out a low milli-voltage signal depending upon the strength of the magnet field. To switch higher voltages the signals need to be amplified and then sent to a power semiconductor. Electromechanical sensors cannot switch very low voltages or currents because they build up films on the contacts with usage. Usually five or more volts are needed to break over this film. They can directly switch up to 240 volts.