Pushbutton keyboard system

A keyboard having a plurality of normally open contact switches, said keyboard comprising:

• a circuit board having first and second sides;
• a plurality of spaced first electrical contacts, each contact extending through said circuit board from said first side of said circuit board to said second side thereof and being electrically connected to selective circuits on said second side;
• a plurality of second contacts, each formed as a curved resilient plate of electrically conductive material spaced from said first contact in a normally open position and having a peripheral edge along at least a portion of which said second contact is supported;
• a contact support on said first side of said circuit board spaced from each of said first contacts and supporting said second contacts along at least a portion of their peripheral edges, said contact support being connectable to a potential, each of said switches completing a circuit upon deflection of the center of said plate from said normally open position to a closed position against a corresponding first contact when pressure is exerted against said center, said center snapping back to said normally open position upon removal of said pressure;
• an insulative element covering said first side of said circuit board to hold said second contacts in position with respect to said first contacts and to keep foreign material out of said contacts, said element including a layer of thin flexible material completely covering said second contacts;
• a plurality of depressible keys;
• and
• means for positioning said keys with one of said keys adjacent each of said second contacts with said layer of flexible material therebetween, each of said keys being selectively depressible to deflect a respective plate from said normally open position to a closed position.