The composition mainly includes shell (1), micro switch (2), adjusting screw (3), push rod (4), plunger (5) and spring (6).

HED1 pressure relay switches the circuit on and off according to the pressure setting value. Circuit terminals are protected by insulating covers (10).

The monitored pressure acts on the plunger (5).

The plunger (5) overcomes the spring force of the steplessly adjustable spring (6), so that the push rod (4) transmits the movement of the plunger (5) to the micro switch (2). This turns the circuit on or off. Mechanical stop (7) protects against excessive pressure.