Electronic Systems TV Typewriter

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Introduced by Electronic Systems in 1977. Bare board $39, complete kit $145.

Very High Resolution Board Photo (460K JPG)
TVT Assembly Manual (670K PDF)
Other Boards Assembly Manuals (520K PDF)

TV TYPEWRITER
This TV Typewriter (TVT) is an ideal addition to any home computer system. It provides one of the most convenient and inexpensive means of getting data in and out of your computer. Among TVT's, one would be hard pressed to find a more versatile unit than this one. The six on-board memory chips will retain 1024 char­acters and spaces. These are arranged as thirty-two lines of thirty-two charac­ters each, with sixteen lines displayed at a time and sixteen held off screen. The cursor which indicates where on the screen the next character will appear, is a flashing white rectangle; but can easily be caused to remain always on (white) or off (transparent). In addition, keyboard controls can move the cursor up, down, left, right, or to home (the upper left-most position on the screen). When the cursor reaches the end of one line, it automatically moves to the beginning of the next. When it reaches the end of the screen it rolls the top line off the screen and moves the rest of the lines up one space to make room for a new line at the bottom. This allows the typist to fill the entire thirty-two lines with text without ever worrying about reaching the end of a line or the bottom of the screen. There are two "scroll" controls to move lines around without moving the cursor. One shifts lines off the bottom of the screen and brings new lines on at the top, while the other shifts them off the top and brings new ones on at the bottom.
 
Single characters can be changed or erased by placing the cursor over them and typing the new character or a space as desired. For larger changes there are "e­rase to end of line" (EOL), and "erase to end of screen" (EOS) controls. The EOL starts at the cursor location and erases all the characters to the end of that line. The EOS starts at the cursor location and erases the rest of the screen, but doesn't touch any of the characters above and before the cursor or the sixteen off-screen lines. The TVT will accept parallel ASCII from a computer output port just as readily as it will from a keyboard. Separate input ports are provided on-board for the computer and the keyboard to make connection easy. A special memory output port is also provided to allow for computer inspection of the on­board memory contents.
 
The TVT logic will also decode and respond to the ASCII codes for carriage return and line feed. This means that the computer can move the cursor around with a single ASCII word, just as easily as printing a character.
 
The output of the TVT is a composite video signal. This means that it contains horizontal and vertical sync signals, as well as blanking and video information. Sync lock and horizontal size and position controls are provided on-board to al­low for easy adjustment, while vertical positioning is handled automatically.
 
In addition to this TV typewriter kit; all that is necessary to complete the sys­tem is an inexpensive video monitor, a keyboard, and a power supply capable of 5 V. at 1.5 A. and -12 V. at 30 mA.


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This page was last edited June 05, 2005