blem, Camras invented the spinning record head. Instead of moving the tape rapidly past the recording head, he moved the tape slowly, and rapidly spun the head. By attaching the head to a 20,000 rpm Hoover vacuum cleaner motor (stolen, by the way, from his wife's vacuum cleaner), he was able to use two-inch tape and reduce the tape transport speed to 30 to 40 inches per second-a dramatic improvement. The first video demonstrations were admirable, but rather funny. First of all, the resolution of the television was only 40 lines per inch, compared to more than 250 on modern systems. The images were so poor that audiences required a narrator to tell them what they were seeing on the screen. Luckily, other advances followed. The original video systems rendered black and white images, but soon a color system was developed. It recorded five tracks (red, blue, green, synch, and audio) on half-inch tape and ran at the original speed of 360 ips. The system was a bit unwieldy: It required a mile of color tape to capture a 4-minute recording. Obviously, mile-long tapes were unacceptable, especially if they would only yield 4-minute programs. As a result, the Sarnoff/Ampex team reex- Downloaded from Digital Engineering Library @ McGraw-Hill (www.digitalengineeringlibrary.com) Copyright © 2004 The McGraw-Hill Companies. All rights reserved. Any use is subject to the Terms of Use as given at the website. Premises Technologies Premises Technologies amined the design of the recording mechanism. Three scientists- Charles Ginsburg, Alex Maxey, and Ray Dolby (later to be known for his work in audio)-redesigned the rotating record head, rotating it about 90 degrees so that the video signal was now written on the tape in a zigzag design. This redesign, combined with FM instead of AM signal modula- tion, allowed the team to reduce the tape speed to a remarkable 17.5 inches per second. For comparison's sake, modern machines consume tape at about 2.5 inches per second. This, by the way, is why the record head in your home VCR sits at a