The Crosby system was an FM
stereophonic broadcasting standard developed by
Murray G. Crosby. In the United States, it competed with, and ultimately lost to, the Zenith/GE system, which the
FCC chose as the standard in 1961.
While both systems used
multiplexing
In telecommunications and computer networking, multiplexing (sometimes contracted to muxing) is a method by which multiple analog or digital signals are combined into one signal over a shared medium. The aim is to share a scarce resource� ...
to transmit the L-R stereo signal, the Crosby system used a frequency-modulated 50 kHz subcarrier, whereas the competing Zenith/GE system used an amplitude-modulated 38 kHz subcarrier. As FM is less susceptible to interference and noise than AM, the Crosby system had better frequency response and less noise of the two systems especially under weak signal conditions. However, the Crosby system was incompatible with existing
subsidiary communications authorization (SCA) services which used subcarrier frequencies including 41 and 67 kHz. These SCA services were used by many FM stations since the mid-1950s for subscription-based "storecasting" to raise revenue and for other non-broadcast purposes. They consequently lobbied the FCC to adopt the Zenith/GE system.
FCC tests in 1960 confirmed that the Zenith/GE stereo system was compatible with 67 kHz SCA operation, although not 41 kHz.
According to Jack Hannold:
On April 19, 1961, the FCC released its Final Order selecting the Zenith/GE system as the FM stereophonic broadcasting standard. At 9:59 AM that day, Crosby-Teletronics stock was worth $15 a share; by 2:00 P.M. it was down to less than $2.50. Another (albeit relatively minor) factor in the FCC choosing the Zenith/GE system was the widespread use of
vacuum tube
A vacuum tube, electron tube, thermionic valve (British usage), or tube (North America) is a device that controls electric current flow in a high vacuum between electrodes to which an electric voltage, potential difference has been applied. It ...
s in radios at the time; the additional tubes for an all-FM system would have increased the size, weight, cost of and heat generated by each tuner or receiver.
References
*Nichols, Roger
I Can't Keep Up With All The Formats 2003 (copy at the Internet Archive).
*Schoenherr, Steven E.
1999-2001 (on the website of the
Audio Engineering Society
The Audio Engineering Society (AES) is a professional body for engineers, scientists, other individuals with an interest or involvement in the professional audio industry. The membership largely comprises engineers developing devices or product ...
)
External links
*Beaubien, William H.
A Report of FM Stereo at the CCIR Study Group X Conference in Bad Kreuznach, GermanyJAES Volume 11 Issue 1 pp. 2–5; January 1963 {{Closed access
Broadcasting standards