| 摘要 |
A secrecy cover for a key pad having a 3x4 matrix of pressure operated depressible keys provides a five-sided casement defining a medial cavity to fit over a matrix of keys of the touch tone key pad to secret entry of one or more sequences of up to three sequential digits of a multidigit number entered into the key pads. The casement face provides at least two lineally arrayed unmarked operator keys that are depressible in predetermined sequence to move one of at least two elongate operator bars of operating mechanism carried within the casement chamber. Each operator bar carries a key depressor movable thereon between at least two alternative positions to depress one potentially depressible key pad key aligned beneath the operator bar. The key depressors are digitally movable by an operator to predetermined positions over a key pad key before placement of the secrecy cover on a key pad. An observer of the operation of the secrecy cover will not know which of the underlying key pad keys are depressed responsive to operation of a particular operator key, to provide secrecy for operation of up to three sequential key pad keys in one operation.
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