"RA-1, Channel One. Special Service Air Channel."
December 1, 2013 10:45 PM   Subscribe

Rockford, IL: So, I made this recording of a mysterious telephone loop in 1991...

I could occasionally summon this message by mashing the touch-tones on an analogue telephone in the late 1980s and early 1990s. "RA" may refer to Rockford Airport, which would explain the notion of a "special service air channel," but that's as close as I can get. It's been a mystery for almost 25 years. Anyone from the area have any explanations, or perhaps remember this message as well?
posted by mykescipark to Technology (6 answers total) 21 users marked this as a favorite
I have no idea what this is, but FWIW it doesn't sound aviation-related to me or to my partner who's been a small plane pilot for 20+ years. There's a variety of automated voice recordings for airport info, but they sound different than this. Also I'd expect the Rockford Airport to identify itself as RFD.

I'm trying to imagine what kind of service you'd reach by generating random touch tones.
posted by Nelson at 8:49 AM on December 2, 2013

I've heard loops similar to this used to keep frequencies "open", i.e. to dissuade anyone else from using your chosen frequency, while making sure that your intended recipient can find your signal and check strength/quality before your actual transmission starts. Most of the ones I've heard have seemed to be TV/radio crews preparing to transmit live segments back to their studios, but I seem to remember hearing some that sounded like they were from my local airports (one civilian, one military), and plenty of others that we could never identify.

You'd expect that to be a radio-only thing, but I've seen references to things like an airport's weather station (a looping broadcast of the latest weather update) being made available by telephone, so people could just dial in to hear whatever the station is currently broadcasting. Maybe it was something like that, a backup for whatever transmissions that frequency was being reserved for?

Speculation aside, you might consider contacting these guys, if you haven't already. It looks like they're the maintainers of the network of radio repeaters that amateurs in IL use to re-transmit their signals, bouncing them further across the state. They need a familiarity with chunks of the local spectrum to do that well, and their hobby involves hunting around for interesting transmissions. If anyone is going to recognise an obscure broadcast or callsign from the area, it's probably them.
posted by metaBugs at 9:17 AM on December 2, 2013

Airport weather info (called ATIS for towered airports, and AWOS or ASOS for untowered airports) is transmitted on radio and also on the telephone. The phone numbers and frequencies can be looked on the FAA document called the Airports and Facilities Directory, abbr. A/FD -- also available on the web at many sites like airnav.com. For example, the San Carlos CA airport weather can be obtained by tuning 125.9 MHz in the Bay Area or by calling 650-593-0613. However your recording is obviously not weather info. It's unlikely to be aviation-related; the "air" might just refer to radio channels.

If you know the phone number you called, you can look it up on the web...
posted by phliar at 9:32 AM on December 2, 2013

Response by poster: If you know the phone number you called, you can look it up on the web...

Well, I didn't reach it by dialing a number; I only reached it by creating strange halftones out of multiple keys at once. This was in 1991, and by the time I graduated from high school (1995), I could no longer reach it.

The idea that it's a repeater is an interesting one. I was a longwave and shortwave radio buff at the same time, and never stumbled across a terrestrial broadcast, but I suppose it could have been up in the UHF/VHF spectrum somewhere. It's certainly not an ATIS or VOLMET station, though.

ILRA is an intriguing possibility. I'll send them a link and see what they have to say.
posted by mykescipark at 10:48 AM on December 2, 2013

Best answer: I asked a someone who knows about these things and he shared what he found out:

"RA" stands for Recorded Announcement and it was used by switching machines made by AT&T. During installation, it was common for Western Electric to populate the RA channels with recordings like that to ensure that they were working and routed correctly.
posted by mogget at 5:16 PM on December 2, 2013 [3 favorites]

Response by poster: Superb! A lifelong mystery resolved. Now all I have to do is figure out the name of the Western Electric engineer from my area... ;-)
posted by mykescipark at 5:27 PM on December 2, 2013

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