Solenoids 'Monostables Series' have a monostable function. By emitting current in the coil, the nucleus is attracted. Arrived in internal stop, it is maintained in the body by a permanent magnet and without power. To bring out the core of the body, the coil will be fed with a reverse current (thus canceling the magnet's field) and an external force (eg spring) will act on the core to bring it back to its original position. In upright position, consider the core weight.