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# Keyboard Self Checking Numbering Method

IP.com Disclosure Number: IPCOM000090378D
Original Publication Date: 1969-Apr-01
Included in the Prior Art Database: 2005-Mar-05
Document File: 2 page(s) / 76K

IBM

## Related People

Marcus, MP: AUTHOR

## Abstract

This self-checking switching matrix controlled by key-operated switches employs logic circuits to simplify the interconnecting circuitry between the keys and to reduce to one the number of contacts on each key. When a given key is depressed in the system employing a modulo-11 counter, it is incremented according to the modulo-11 weight of the given key. When all keys are scanned, a 0 modulo count exists in the counter, providing the inserted number is a valid number. Other modulo systems can be used with this circuitry by substituting other weighted values.

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Keyboard Self Checking Numbering Method

This self-checking switching matrix controlled by key-operated switches employs logic circuits to simplify the interconnecting circuitry between the keys and to reduce to one the number of contacts on each key. When a given key is depressed in the system employing a modulo-11 counter, it is incremented according to the modulo-11 weight of the given key. When all keys are scanned, a 0 modulo count exists in the counter, providing the inserted number is a valid number. Other modulo systems can be used with this circuitry by substituting other weighted values.

As in A, the matrix is based on the columns being premultiplied by the proper weighing factor in the modulo-11 system. For example, the weighted number for key 8 in digit columns 5 and 11 is seven. Likewise, weighted number 4 in digit columns 6 and 12 is indicative of key 8.

Drawing B includes free-running oscillator 1 that is constantly stepping along an eleven-position weight ring 2 that is cycling repeatedly from T...0. Each time ring 2 reaches 0, column ring 3 is advanced one position in a descending order from 13...1. Ring 2 is gated to stop at weight 0 column 1 and is gated to reset and start upon receipt of an external start signal. Ring 2 is a closed type. Ring 3 is of the open type. The output pulse ring 2, in addition to advancing ring 3, also resets latch 4. The outputs of all the key And's are fed to Or 5 whose output is fed to latch 4 to turn it on. When latch 4 is on, pulses from oscillator 1 and ring 2 enter modulo-11 counter 7 via And 6. These pulses advance counter 7 by the weighted value of the key depressed.

Each key is provided with a single contact which is closed when the key is depressed. Each ring 3 line output serves as a common fo...