Unconstrained keyword spotting using phone lattices

A switching module for a solid-state keyboard or the like comprising an actuating key manually movable between a first and a second position and a variable capacitor. The capacitor has a rigid stationary electrode and another electrode movable toward and away from the stationary electrode between a first position in which the electrodes are separated by an air gap and a second position in which the air gap is substantially eliminated for effecting a change in capacitance of the variable capacitor. The movable electrode has a rigid dielectric member secured thereto on its side toward the stationary electrode, this dielectric member having a dielectric constant substantially greater than air. The switching module further comprises a cam coupling the actuating key and the movable electrode for effecting movement of the movable electrode and the dielectric member between their first and second positions in response to movement of the actuating key between its first and second positions.