Key switch

A key switch comprising:

• a housing;
• two permanent magnets accommodated in said housing with their respective opposite poles facing each other and with a gap left between these poles;
• a key rigidly connected with said permanent magnets for reciprocation therewith relative to said housing;
• a switching member secured in said housing to be acted upon by said permanent magnets as said key is displaced;
• a plate of a ferromagnetic material defining a means for retaining said key in its initial position, secured in said housing intermediate said key and said permanent magnets;
• three plates of a ferromagnetic material, arranged in said housing in the direction of reciprocation of said key, defining a magnetic circuit jointly with said plate of said key-retaining means, and defining a means for returning said key into the initial position thereof, one of said three plates being received in said gap between said respective opposite poles of said permanent magnets, and the remaining two plates of said three plates being situated adjacent to the respective other poles of said magnets, with a gap relative to said poles, the length of at least one of said three plates in the direction of reciprocation of said key being short of the sum total of the value of the maximum displacement of said key and the extent of the respective one of said permanent magnets in this direction.