Contactless keyboard

Details Contactless keyboard Contactless keyboard

1981-06-18

1983-08-09

Robinson, Thomas A.

Communications: electrical

Audible indication

Percussion-type sound producer

336110, H03K 1300, G06F 302

Patent

active

043981801

ABSTRACT:
In a contactless keyboard including for each key a transformer with a core displaceable by the key operation and including a compensation transformer common to all key the compensation transformer is so designed that with an unactuated key the signal component of the compensation transformer in the signal applied to the evaluation circuit exceeds the component of the key transformer, whereas with an actuated key the signal component of the key transformer predominates. Therefrom results a phase change of the signal applied to the evaluation circuit with the actuation of a key. The evaluation circuit compares the phase of the key output signal with that of a reference signal. For increasing the immunity from disturbance the evaluation circuit delivers an output signal (key operated or key nonoperated) only when several successive comparison operations give the same result.

REFERENCES:
patent: 3623081 (1971-11-01), Scarbrough
patent: 3911429 (1975-10-01), Vinal
patent: 4283714 (1981-08-01), Trenkler et al.

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