Browse Prior Art Database

Improving Alphanumeric Displays on TV Monitors

IP.com Disclosure Number: IPCOM000082081D
Original Publication Date: 1974-Oct-01
Included in the Prior Art Database: 2005-Feb-28
Document File: 3 page(s) / 48K

Publishing Venue

IBM

Related People

Cannon, JW: AUTHOR

Abstract

Frequency restrictions associated with state-of-the-art televisions for alphanumeric character displays are accommodated, by controlled dot matrix Z-modulation from a read-only storage (ROS) and shift register. The quality of alphanumeric character displays on a TV monitor is restricted, by the maximum Z-modulation frequency at which the video response falls below 3 db, as well as being restricted by the change in video response for a given change in the modulation frequency.

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Improving Alphanumeric Displays on TV Monitors

Frequency restrictions associated with state-of-the-art televisions for alphanumeric character displays are accommodated, by controlled dot matrix Z- modulation from a read-only storage (ROS) and shift register. The quality of alphanumeric character displays on a TV monitor is restricted, by the maximum Z-modulation frequency at which the video response falls below 3 db, as well as being restricted by the change in video response for a given change in the modulation frequency.

For point-to-point unblanking with maximum character density per line, the system must frequently be operated at the greatest distortion from response change for a given frequency change. For instance, the upper bar of a "T" will appear brighter than the adjacent vertical components making up the remainder of the letter. The use of a dot matrix unblanked display permits use of the same fundamental frequency for all horizontal and vertical segments of characters, but this fundamental frequency is often 5 to 10 times the lowest fundamental frequency composing a specific character.

Random-access storage 10 stores the characters in a convenient digital format such as EBCDIC. Storage 10 feeds the read-only storage (ROS) 12 which acts as a character generator and, in turn, loads shift register 14. The output of 14 ultimately becomes the Z-modulation signal at output 20 to be fed to the video monitor or line driver. The frequency of clock 15 is selected depending on the display parameters, such as the number of characters per line, type of display, etc. and directly controls register 14.

Divide N circuit 16 controls the loading of 14 and the incrementing of the storage address register (SAR). N is selected depending on the number of time units within the horizontal spacing of a character position. SAR LO 17 is selected by the number of characters per lin...