Series PM diaphragm pressure switches are available with NC (normally closed) contacts and with NO (normally open) contacts. Series PM681 pressure switches with setting visual scale comply with EN60730 standards and are suitable for signaliing pressure through a normally closed Reed contact. A regulating screw, which can be adjusted using a small screwdriver, allows the switch to be set to the required pressure. The calibrated diaphragm enables an electrical signal to be generated or inhibited depending on the pressure set.