[EAS] Making a better alerting system

[Lamm, Dale]

[snip]

The two tones came from AT&T Bell Labs in the early 70s based on their research including no conflicts with other tones used at the time and the signals uniqueness. Industry tested the signal before the FCC adopted the signal in 1976 along with an expansion of the EBS into State and Local warning.

[end]

The discordant 853/960 Hz pair contains frequencies NOT in a common musical scale. Each tone is centered between two "legal" notes (G# and A, A# and B), so the chance of conventional music tripping a detector is minimized.

IMO, decades of use and substantial penalties for their misuse has made this pair of tones unique. Why else would advertisers and promoters keep trying to slip them into productions? Were they invented today, someone would probably try to patent or trademark them.

Humorous note: Bringing an SBE meeting to order can be difficult. Playing 853/960 on a cell phone instantly causes a roomful of broadcast engineers to shut up.

Dale Lamm
WHBC AM & FM