Abstract: Keypads are described which are row similar to a standard telephone keypad though they have a different number of columns of base-letter-assigned keys than the standard to which they are related. Smooth sequences of such row-similar keypads are exhibited. Keypads which support both row-similar telephone keypad layouts and reduced layouts corresponding to typewriter standards are disclosed. It is shown how to combine various structural and statistical limitations with row similarity. It is also shown how to embed a row-similar digit layout in row-similar base letter layouts, and how to beneficially provide negative space between keys, construct pseudo standards, and extend or reduce desktop standards or pseudo standards while obeying structural or typability constraints.

Abstract: An ambiguous keyboard has three to five columns and at least three rows of keycaps, each with three actuators arranged in a triangle. At least nine keycaps have a digit entry portion at either the keycap's top or bottom portion, a number digit, an actuator and a sensor. At least nine keycaps have left and right non-digit symbol entry portions. A plurality of the keycaps have at least one non-digit symbol assigned to them. Pressing the right non-digit symbol entry portion activates the sensor for the right non-digit symbol entry portion and pressing on the left non-digit symbol entry portion activates the sensor for the left non-digit symbol entry portion.

Abstract: Keypads are described which are row similar to a standard telephone keypad though they have a different number of columns of base-letter-assigned keys than the standard to which they are related. Smooth sequences of such row-similar keypads are exhibited. Keypads which support both row-similar telephone keypad layouts and reduced layouts corresponding to typewriter standards are disclosed. It is shown how to combine various structural and statistical limitations with row similarity. It is also shown how to embed a row-similar digit layout in row-similar base letter layouts, and how to beneficially provide negative space between keys, construct pseudo standards, and extend or reduce desktop standards or pseudo standards while obeying structural or typability constraints.