Abstract: A capacitive keyboard verification system is disclosed wherein key movement is verified with a high degree of accuracy in a manner largely immune to ambient noise or other electronic or electromagnetic interference. A pulse signal, in the form of a train of pulses, is periodically applied across the capacitor associated with each key. The signal coupled through the capacitor is reconstructed only if it exceeds a predetermined reference level. A test, which depends on the previously verified key state, is made to determine the existing key state. The test for the active key state is conditioned on multiple true comparisons of a reconstructed signal with the originally applied signal throughout the duration of the test. The test for the inactive key state is conditioned on the absence of a reconstructed signal throughout the test. In both instances the newly indicated key state is compared with the state to which the key is assumed to have changed from its previously verified state.