Triangular Toggle Keys for Touch-Tone Phones
Original Publication Date: 1988-Jun-01
Included in the Prior Art Database: 2005-Feb-15
This article describes a method of getting multiple distinguishable outputs from a single telephone button. It allows a specific letter of the alphabet to be entered into a phone, without increasing the number of buttons on a standard phone. It also allows standard numbers to be entered. The increasing need to key letters as well as numbers using touchtone keys motivates the transformation of the 12 traditional square keys to the triangular keys described. The problem solved is the ability to use the push-button telephone as a general input device, without having the ambiguity of which of three letters a particular button stands for and how to distinguish between number entry and alphanumeric entry. Hardware Implementation Fig. 1 shows the finger-actuated key and printed circuit board for a telephone dial.