Pushbutton telephone subscriber's apparatus in which there is provided a light pen arrangement for reading printed bar-code patterns representing series of decimal digit values, such as telephone numbers, and for converting the signal voltages obtained from reading these patterns to a form which can...http://www.google.com.hk/patents/US4042792?utm_source=gb-gplus-share專利 US4042792 - Telephone subscriber's apparatus for signalling decimal digit values represented in printed form
