Ternary chord-type keyboard

Described is a data entry keyboard having a small number of keys, each key being a ternary device having three possible positions. In the preferred embodiment, each key is adapted to move towards or away from the operator, and has a central "off" position. A spring detent makes the key return to the central position in the absence of pressure from the finger. The three positions of each key are indicated electrically by switches which produce distinctive signals for each of the three states. The top of each key is formed to provide a secure grip. The preferred embodiment comprises eight ternary keys in two sets of four. The two sets are arranged so that the fingers of the operator's right hand rest on the keys of a rightmost set, and the fingers of the operator's left hand rest on the keys of the leftmost set. The only key combinations which represent valid characters are those in which one finger of the right hand operates its key, and one finger of the left hand operates its key. With this scheme of coding, there are 64 possible keyboard states to represent valid characters: all other states are ignored or used as delimiters. This keyboard does not require movement of the fingers from one key to another, and requires only ordinary skill and care on the part of an operator to avoid unwanted states during transitions from one character to the next.