lash@tellabs.com (Bill Lash) (02/19/91)
I got several requests to post the information that I got concerning getting stock ticker information from FM, so I will post a summary. I am keeping the respondents anonymous so that their mailboxes won't overflow, but I would like to thank them all. A few people questioned the legality of doing this. I was initially under the impression that this was a service of the FM station, but most people think that it is a pay service that can be subscribed to. If it is a pay service, it may be at least ethically questionable to take the data without paying for the service. It probably also implies that the data is scrambled and/or the encoding scheme is unpublished and proprietary. I had one response talking about a pay service in the Chicago area, (where I am), called Quotrex. I believe this a beeper like device over which you can get quote information. The same person believes that Lotus sells a device which can receive this data and import it directly to Lotus 1-2-3. Another response said " Try contacting DATARx 111 E. Drake Rd., Suite 7041 Fort Collins, Colorado. They make kits and software packages to do the kind of thing that you propose." ... " Oh, the phone number of DATARx is (was) 303-223-2120". I have not tried contacting them yet, but this looks promising. A response posted to Comp.sys.ibm.pc.hardware said: " There's a company called Express which sells hardware for doing this off cable TV using a sideband (like the alternate language coverage). If that's what is carried in your area they may sell a tuner for that, too. You pay a one time <$100 charge for the modem, data is free. I'm looking into the data format, I want to catch it with a UNIX box doing other stuff, not a dedicated PC." To tell you the truth, this may be what I was thinking about to begin with. I seem to remember getting information from my cable company about this a while back. Someone else replied: "FNN in LA has a service that reads the QuoTrek info - you might contact them. I think they call their service "X-Press". I've seen adds for it several times on FNN but dont have the 800 number." This sounds like it could be the same thing as above. Another response gave a description of how this data is encoded along with an FM radio station's normal signal. This would require a lot of reverse engineering on my part, and if I had the time it might be a fun project, but I don't have the time now. Here is the information. "It is usually broadcast as a subcarrier on an FM broadcast station. If you look at the signal coming out of the demodulator of your FM radio, it looks like: 0------------------19 KHz --------------- 38 KHz ------------- 68 KHz Mono audio tone L-R for stereo tone SCA subcarriers So that if you use a standard FM radio that cuts off everything about 19 KC or so, you just get good mono audio, and if you use a stereo radio, it mirrors down the L-R difference signal and uses it to generate the stereo pair. The stuff from 38 to 68 KHz is often used for reading services for the blind, special-purpose pay-radio services, Muzak distribution, and various digital radio services. If you tune to a station in stereo with a slightly imperfect receiver and pick up whistling noises in the background, it's probably the SCA subcarrier leaking into the audio, with some digital stuff being broadcast. Usually the digital services are 4800 baud with QPSK modulation, but not always, and they tend to use a variety of frequencies for their carrier. If you can get an SCA receiver and a scope it should not be difficult to reverse-engineer things." Again, thanks to all who responded. Bill Lash lash@tellabs.com ...!uunet!tellab5!lash