GB1492538A - Keyboards - Google Patents

Abstract

1492538 Keyboards with coded outputs LOUGHBOROUGH CONSULTANTS Ltd 7 March 1975 [8 Dec 1973 4 March 1975] 57009/73 and 8987/75 Heading G4H A keyboard contains logic circuitry which operates in such a way that simultaneous depression of two or more keys gives rise to a signal which represents a character different from that obtained when only one key is depressed. The extra character may be indicated by marks placed between or across the keys which are arranged to facilitate simultaneous depression with one finger. In the embodiment of Fig. 1, a decimal keyboard contains four keys 1, 3, 7 and 9. Codes for, e.g. the number 2À are obtained by pressing, e.g. keys 1 and 3, while depression of all four keys gives the code for 5. Each key (Fig. 1) is connected to a circuit (Fig. 3, not shown) having complementary outputs (e.g. 1, T) which are fed to a logic circuit, Fig. 4, which produces a BCD output for the required character. The output is also fed to a 7-segment decimal display controlled by a blanking circuit (Fig. 5, not shown) which keeps the display inoperative while no key is depressed, and also for a short period following the depression of a key to ensure that only one number is displayed even though a key combination is not pressed simultaneously. Other examples of alphabetic and alphanumeric keyboard layouts are also illustrated.