TV Typewriter
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The TV Typewriter was a video terminal that could display 2 pages of 16 lines of 32 upper case characters on a standard television. The Don Lancaster design appeared on the cover of Radio-Electronics magazine in September 1973. The magazine included a 6 page description of the design but you had to send off for a 16 page package of construction details. Radio-Electronics sold thousands of copies for $2.00 each. The TV Typewriter is considered a milestone in the home computer revolution along with the Mark-8 and Altair 8800 computers.
Don Lancaster's day job was at Goodyear Aerospace and they were designing a high resolution video display that gave Don the inspiration to design a low cost TV Typewriter. The design used TTL digital logic and shift register memory. (Microprocessors and RAM were new and very expensive.) With professional terminals costing over $1000 this $120 kit looked like a bargain.
SWTPC sold the circuit boards but never offered a complete kit. Many parts were hard to find and the compact design made this a challenging project. The original design did not include a serial port or keyboard. In 1974 Don designed a keyboard board kit. A serial port was designed by Roger Smith and appeared in the February 1975 issue of Radio-Electronics.
Ed Colle was an engineer who had designed a 2000 character 300 kilowatt message board. Previously Ed had worked at Datapoint on terminal design so he made an 80 character by 25 line terminal for the sign board. Daniel Meyer saw the terminal and asked Ed to design a terminal for SWTPC.
The SWTPC CT-1024 Terminal displayed 32 characters by 16 lines without scrolling. It used common TTL parts and 2102 static RAMS. The boards were laid out with very loose part spacing and wide traces to make it easy to assemble. A complete set of option boards were offered including a serial interface. The keyboard was Don Lancaster’s design. The rest of the terminal was done by Ed Colle.
The design was finished by July of 1974 and submitted to Radio-Electronics. It was featured as the TV Typewriter II. It was finally offered for sale in January 1975. It was very successful because a complete kit with options cost only $275. It was replaced in 1977 by the improved CT-64 that offered scrolling and 64 character per line of upper and lower case.
Contents |
[edit] TV Typewriter Cookbook
By 1975 Don Lancaster had authored a hundred articles in magazines such as Popular Electronics and Radio-Electronics. He had also written a digital design book titled the RTL Cookbook in 1968. Resistor-transistor logic (RTL) was an early IC technology that was replaced by TTL, so in 1974 he published the TTL Cookbook. This book was in print for 20 years and sold a million copies.
The original TV Typewriter was designed before low cost RAM was available and the design was soon obsolete. Don had made many design improvements and published them as the TV Typewriter Cookbook in 1976. Portions had been serialized in the first issues of Byte magazine. The book was a guide on how to design a video computer terminal; it did not just give a single design example.
- Chapter 1. Some Basics.
- Chapter 2. Integrated Circuits for TVT use.
- Chapter 3. Memory.
- Chapter 4. System Timing - Calculation and Circuits.
- Chapter 5. Cursor and Update Circuits
- Chapter 6. Keyboards and Encoders.
- Chapter 7. Serial Interfaces.
- Chapter 8. Television Interfaces.
- Chapter 9. Hard Copy and Color Graphics.
This book guided many hobbyist and professionals in designing video displays for home computer systems. The cassette interface design from chapter 7 was the basis for the Kansas City Standard. The circuits in this book did not rely on a microprocessor, just TTL logic. The TV Cheap Video Cookbook (1978) showed the TVT 6 5/8 that would work with a 6502 or 6800 microprocessor. The design was targeted at the KIM-1 Microcomputer.
The TTL Cookbook and The TV Typewriter Cookbook could be found in every computer store in 1976 and 1977.
[edit] TV Typewriter gallery
Click the images to enlarge.
 Computer History Museum |
 SWTPC Keyboard |
 CT-1024 Terminal with monitor |
 CT-1024 Terminal System |
[edit] References
Lancaster, Don (1969). RTL Cookbook, First edition, Indianapolis, IN: Howard W. Sams. ISBN 0-672-20715-X.
Lancaster, Don (1974). TTL Cookbook, First edition, Indianapolis, IN: Howard W. Sams. ISBN 0-672-21035-5.
Lancaster, Don (1976). TV Typerwriter Cookbook, First edition, Indianapolis, IN: Howard W. Sams. ISBN 0-672-21313-3.
Lancaster, Don (1978). The Cheap Video Cookbook, First edition, Indianapolis, IN: Howard W. Sams. ISBN 0-672-21524-1.
Lancaster, Don (September 1973). "TV Typewriter". Radio-Electronics 44 (9): 43-52.
Lancaster, Don (April 1974). "ASCII Keyboard and Encoder". Popular Electronics 5 (2): 27-31.
Colle, Ed (February 1975). "TV Typewriter II". Radio-Electronics 46 (2): 27-30.
Smith, Roger (February 1975). "Uart and Modem for TV Typewriter". Radio-Electronics 46 (2): 51-53.
