into the helical scanning technique used in virtually all video tape machines, such as those using the consumer formats of VHS, Sony Betamax and Video 2000. Sony Betacam was successful as a professional format but operated with a different recording system and faster tape speed than Betamax. One of the key engineers in the development of the Quadruplex video recorder for Ampex was Ray Dolby, who worked under Charlie Ginsburg and went on to form Dolby Laboratories, a pioneer in audio noise reduction systems. Dolby's contribution to the videotape system was limited to the mathematics behind the reactance tube FM modulator, as videotape then used FM modulation for the video portion. Another contributor designed the FM modulator itself. Dolby left Ampex to seek a PhD in physics in England, which is where Dolby Labs was later founded, before moving back to San Francisco. Dolby's brother Dale was also an engineer at Ampex. VR-5000 and VR-8000 In 1961, Ampex introduced the first 1-inch helical scan video recorders, the Ampex 2-inch helical VTRs, which recorded video using helical scan recording technology on tape. Ampex 2-inch helical VTR Ampex 2 inch helical VTRs were manufactured from 1963 to 1970. Model VR-1500 for home. The VR-660 for Broadcast television systems, industrial companies, educational institutions, and a few for In-flight entertainment. The VR-1500 and VR-660 found service at educational institutions especially due to their relatively low cost vs. quadruplex VTRs. These machines were simple to operate, reliable, small in size and produced, for their time, very good video without the complexity of the larger and much more complex 2" Quad machines. HS-100 & HS-200 "slo-mo" disc recorder In March 1967, Ampex introduced the HS-100 video disc recorder. The system was developed by Ampex at the request of the American Broadcasting Company (ABC) for a variety of sports broadcast uses. It was first demonstrated on the air on March 18, 1967, when ABC's Wide World of Sports televised the "World Series of Skiing" from Vail, Colorado. The video was recorded on analog magnetic disc. The disc weighed and rotated at 60 rps, 3600 rpm (50 rps in PAL). One NTSC unit could record 30 seconds of video, PAL units 36 seconds. The video could then be played back in slow motion, stop action to freeze frame. A more deluxe version, the HS-200, was introduced in April 1968, and provided a large control console with variable speed