Browse Prior Art Database

Touch Sensitive Capacity Switch Circuit

IP.com Disclosure Number: IPCOM000076777D
Original Publication Date: 1972-Apr-01
Included in the Prior Art Database: 2005-Feb-24
Document File: 2 page(s) / 34K

Publishing Venue

IBM

Related People

Kolias, JT: AUTHOR [+2]

Abstract

This circuit is constructed so that capacitor 10, resistor 11 and body capacitance form a capacitive voltage divider across the sixty cycle AC supply from transformers 12. When the contact 13 is touched, the capacitance of the human body completes the voltage divider circuit and raises the voltage across capacitor 10 to a level which exceeds the breakover potential of neon tube 14. The capacitor 10 and the human body then discharge into the base of the amplifier transistor 15. The amplified discharge current flows into capacitor 16 and is further amplified by circuit 17 to operate a single-shot 18, which in turn provides an activating signal to suitable logic circuits associated with a data-processing system.

This text was extracted from a PDF file.
At least one non-text object (such as an image or picture) has been suppressed.
This is the abbreviated version, containing approximately 96% of the total text.

Page 1 of 2

Touch Sensitive Capacity Switch Circuit

This circuit is constructed so that capacitor 10, resistor 11 and body capacitance form a capacitive voltage divider across the sixty cycle AC supply from transformers 12. When the contact 13 is touched, the capacitance of the human body completes the voltage divider circuit and raises the voltage across capacitor 10 to a level which exceeds the breakover potential of neon tube 14. The capacitor 10 and the human body then discharge into the base of the amplifier transistor 15. The amplified discharge current flows into capacitor 16 and is further amplified by circuit 17 to operate a single-shot 18, which in turn provides an activating signal to suitable logic circuits associated with a data- processing system. Capacitor 16 is designed to function as a high-pass filter and allows only the touch-generated high-frequency signal to pass through it, while it inhibits passage of the low-frequency sixty cycle AC signal when the contact 13 is not activated by touch.

This circuit is particularly useful in connection with contacts located on the face of a cathode-ray tube (CRT) display tube having plural such contacts which may be activated by touch. The contact arrangement is preferably in the form of a transparent dielectric material which overlays the CRT in a predetermined pattern, and the CRT projects keyboard or selection type data from the computer at CRT positions corresponding to the organization of the contacts.

1

Page 2 of...