F5 pressure switches activate a microswitch once a preset pressure value is reached. The preset pressure is set by rotating the internal screw located at the center of the instrument. The internal screw is accessible by removal of the protection plug, clockwise to increase and vice-versa to decrease the value. Mechanical stops protect both the spring and microswitch from over pressurization. In F5-P version for the regulation is necessary to operate in the same way on the knob apposite with locking screw. Of compact and economical construction, it is suitable for system not requiring a constant alteration.