veeneman@mot.com (Dan Veeneman) (11/28/90)
I just got back from a long weekend trip to Baltimore, and during a delay due to "mechanical problems" I got a chance to peek at the GTE Airfones that were built into the headrest of the center seats of each row. Inserting a credit card into a vertical slot released the phone, which was tied to the headrest by a short (two or three foot) cord. Sliding a credit card along the right edge of the handset would, after a short time, give you the opportunity to place your call. (I only got a chance to observe, as the phone in my row was non-functional, much to the disappointment of the guy next to me). Hopefully someone out there will have the answers to these questions: 1. How is the credit card verified ? Are they all stored on board and downloaded after the airplane lands, or is it real-time ? 2. What happens if everyone wanted to place a call at the same time? On the jet I was on, that would be 56 phones in use at the same time. Quite a multiplexer/transceiver, if that's how it's done. 3. How is frequency assignment done for numerous planes in the same local area (i.e. 20 planes backed up, waiting for takeoff at O'Hare)? 4. Has anyone tried a ringback or number announcement from the phone ? I know the phones aren't capable of actually receiving a call or ringing, but it would be interesting to see what happens. 5. Is there a nationwide cellular-like network for these phones, i.e. the ground station hands off the call(s) to the next station when the plane leaves the service area ? Any further information would be appreciated. Dan veeneman@Mot.Com
covert@covert.enet.dec.com (John R. Covert 29-Nov-1990 1017) (11/30/90)
>1. How is the credit card verified ? Are they all stored on board >and downloaded after the airplane lands, or is it real-time ? I'm 99% sure it's real-time, done during call setup. >2. What happens if everyone wanted to place a call at the same time? >On the jet I was on, that would be 56 phones in use at the same time. >Quite a multiplexer/transceiver, if that's how it's done. Only a small number of phones can be in use at one time. Other callers will get a recording telling them "Please wait for the dial tone." >3. How is frequency assignment done for numerous planes in the same >local area (i.e. 20 planes backed up, waiting for takeoff at O'Hare)? Similar to land-based cellular phones. However, Airfone is not supposed to work on the ground. There may be airports close enough to airfone cell sites that it works at some of them, but it is an "in-flight" service. >4. Has anyone tried a ringback or number announcement from the phone >? I know the phones aren't capable of actually receiving a call or >ringing, but it would be interesting to see what happens. Those sort of numbers are blocked. The phone accepts only NPA-NXX-XXXX or 011+CC+... >5. Is there a nationwide cellular-like network for these phones, i.e. >the ground station hands off the call(s) to the next station when the >plane leaves the service area ? There is a nationwide network, but there is no hand-off. john
gt6392b@prism.gatech.edu (Fish Dude) (12/04/90)
In article <15124@accuvax.nwu.edu> covert@covert.enet.dec.com (John R. Covert 29-Nov-1990 1017) writes: >>4. Has anyone tried a ringback or number announcement from the phone >>? I know the phones aren't capable of actually receiving a call or >>ringing, but it would be interesting to see what happens. >Those sort of numbers are blocked. The phone accepts only >NPA-NXX-XXXX or 011+CC+... What about 1-800 numbers? What will an ANI display show as the orgin of the call? As Always, Mark D. Fisher (404) 352 1452 GT Box 36392, Atlanta Georgia, 30332 gt6392b@prism.gatech.edu
seanp%undrground@amix.commodore.com (Sean) (12/05/90)
> 1. How is the credit card verified ? Are they all stored on board > and downloaded after the airplane lands, or is it real-time ? Dan- When you insert your credit card, the information (number, exp. date, etc. ) is sent via 300 baud signal to a ground station. (REAL TIME). The ground station then confirms or denys usage, and proceeds from there. Actually, the handset is not released until then card is approved. > 2. What happens if everyone wanted to place a call at the same time? > On the jet I was on, that would be 56 phones in use at the same time. > Quite a multiplexer/transceiver, if that's how it's done. The transmitter section of the setup is IMPRESSIVE. Everyone could concievably use thier phone at the same time, as there are 400 channels available for use. This concept applies only, however, to one ground station. There are 80 ground stations in the U.S., though. > 3. How is frequency assignment done for numerous planes in the same > local area (i.e. 20 planes backed up, waiting for takeoff at O'Hare)? Frequency assignment goes something like this: 894 - 896 MHz (5 KHz spacing). Assignment is done in the same manner as cellular. It picks an available frequency from what the ground station tells it. AM mode is used for modulation. > 4. Has anyone tried a ringback or number announcement from the phone > ? I know the phones aren't capable of actually receiving a call or > ringing, but it would be interesting to see what happens. This would give the same result as doing it from any other phone, as in the end, you are connected with the P.S.T.N. > 5. Is there a nationwide cellular-like network for these phones, i.e. > the ground station hands off the call(s) to the next station when the > plane leaves the service area ? You are absolutley correct. Handing off and signal comparison is done in much the same way. Really, however, you would have to talk for quite a while in order to leave a service area. Consider transmitting with high power, at 35,000 feet. Most planes out of Philadelphia can hit Atlanta radio right after takeoff, with good/excellent quality. Hope this helps. Sean Petty INTERNET: seanp%undrground@amix.commodore.com UUCP: ...{rutgers|uunet|etc..}!cbmvax!amix!undrground!seanp
rees@pisa.ifs.umich.edu (Jim Rees) (12/07/90)
In article <15223@accuvax.nwu.edu>, seanp%undrground@amix. commodore.com (Sean) writes: >The transmitter section of the setup is IMPRESSIVE. Everyone could >concievably use thier phone at the same time, as there are 400 >channels available for use. I doubt very much that the airplane is able to transmit on 400 channels, or even 56 channels, at once. >894 - 896 MHz (5 KHz spacing). Assignment is done in the same >manner as cellular. It picks an available frequency from what the >ground station tells it. AM mode is used for modulation. AM on 5KHz spacing? Are you sure? I would guess companded SSB, just based on the age of the system, but I don't know. We have now had one person claim that there is no hand-off, and another claim that there is. What's the real story? Airfone pre-dates cellular, right?
kam@dlogics.COM (Kevin Mitchell) (12/08/90)
In article <15223@accuvax.nwu.edu>, seanp%undrground@amix.commodore. com (Sean) writes: > When you insert your credit card, the information (number, exp. > date, etc. ) is sent via 300 baud signal to a ground station. (REAL > TIME). The ground station then confirms or denys usage, and proceeds > from there. Actually, the handset is not released until then card is > approved. Is the data encrypted? It sounds like a massive security leak, broadcasting sensitive information about a card like that. I know all the arguments about privacy, not listening to certain frequencies, etc., but a credit card pirate with an all-band receiver isn't going to be "nice" about it. > 894 - 896 MHz (5 KHz spacing). Assignment is done in the same > manner as cellular. It picks an available frequency from what the > ground station tells it. AM mode is used for modulation. This is different from what I've heard. Popular Electronics has a scanner column, and reported several 470 MHz band frequencies where you can pick up air phone calls. I've found some there. Kevin A. Mitchell (312) 266-4485 Datalogics, Inc Internet: kam@dlogics.UUCP 441 W. Huron UUCP: ..!uunet!dlogics!kam Chicago, IL 60610 FAX: (312) 266-4473
zippy@chaos.cs.brandeis.edu (Patrick Tufts) (12/11/90)
Additional Musings on the GTE Airfone. According to the original post, it sends your credit card info at 300 baud somewhere for verification. Additionally, it transmits calls between 894MHz and 896 MHz (5kHz spacing). Does this mean that anyone with a scanner and a modem can grab hundreds of credit card numbers, expiration dates, ... Or is the card info encoded before transmission? Pat
seanp%undrground@amix.commodore.com (Sean) (12/11/90)
> >The transmitter section of the setup is IMPRESSIVE. Everyone could > >concievably use thier phone at the same time, as there are 400 > >channels available for use. > I doubt very much that the airplane is able to transmit on 400 > channels, or even 56 channels, at once. If they weren't able to do it, then they would limit the number of phones that were placed aboard the plane. If, however, four planes on the same runway all tried to use all of thier phones, a SERVICE UNAVAILABLE message would be generated, much like cellular. > >894 - 896 MHz (5 KHz spacing). Assignment is done in the same > >manner as cellular. It picks an available frequency from what the > >ground station tells it. AM mode is used for modulation. > AM on 5KHz spacing? Are you sure? I would guess companded SSB, just > based on the age of the system, but I don't know. Yes, AM is used on the following ranges (Newer AIRFONES use 6 KHz space) 849 to 851 894 to 896 899 to 901 and 944 to 946 And, for future reference, it is COMPANDORED. As in, AMPLITUDE COMPANDORED SINGLE SIDEBAND. Really, this technology would be unrealistic for air use. With the ever changing conditions, ACSSB would be extremely difficult to maintain a tuned carrier. This was the case when United Parcel Service considered implementing ACSSB. The company selling them the radios concluded that that technology would require too much operator control and tuning, thus requiring more in-depth training about the radios. And this was for GROUND use, AIR is even worse. > > When you insert your credit card, the information (number, exp. > > date, etc. ) is sent via 300 baud signal to a ground station. (REAL > > TIME). The ground station then confirms or denys usage, and proceeds > > from there. Actually, the handset is not released until then card is > > approved. > Is the data encrypted? It sounds like a massive security leak, > broadcasting sensitive information about a card like that. I know all > > 894 - 896 MHz (5 KHz spacing). Assignment is done in the same > > manner as cellular. It picks an available frequency from what the > > ground station tells it. AM mode is used for modulation. I never attempted to decipher it. I would imagine it should be, but stranger things have happened! > scanner column, and reported several 470 MHz band frequencies where > you can pick up air phone calls. I've found some there. I have yet to hear of AIRFONE signals in that band. Perhaps you are thinking of the 415.7 MHz frequency for government VIPS? If not, tell me what frequencies and modes, please. Sean
carroll@cs.washington.edu (Jeff Carroll) (12/19/90)
In article <15300@accuvax.nwu.edu> rees@citi.umich.edu (Jim Rees) writes: >In article <15223@accuvax.nwu.edu>, seanp%undrground@amix. >commodore.com (Sean) writes: >>The transmitter section of the setup is IMPRESSIVE. Everyone could >>concievably use thier phone at the same time, as there are 400 >>channels available for use. >I doubt very much that the airplane is able to transmit on 400 >channels, or even 56 channels, at once. I would also doubt that you could operate 400, or even 56, independent radio channels from the same bird. Even doing 25 (as we have on AWACS) results in horrendous self-jamming and elaborate frequency allocation software, not to mention hundreds if not thousands of pounds of antenna couplers. On the other hand, a recent conversation with the manager responsible for integrating the equivalent of AirFone into our next generation airplane left me with the impression that there was quite a big chunk of bandwidth required. One obvious solution would be an onboard DS1 mux which performs upconversion at its output to an IF frequency of the UHF set (most likely 70 MHz). I don't know whether such a beast exists today, but I doubt that that's what is used in most AirFone installations (i.e. one phone in the back of the plane). Jeff Carroll carroll@atc.boeing.com
riddle@hoss.unl.edu (Michael H. Riddle) (12/20/90)
In <15520@accuvax.nwu.edu> bcsaic!carroll@cs.washington.edu (Jeff Carroll) writes: > I would also doubt that you could operate 400, or even 56, >independent radio channels from the same bird. Even doing 25 (as we >have on AWACS) results in horrendous self-jamming and elaborate >frequency allocation software, not to mention hundreds if not >thousands of pounds of antenna couplers. > On the other hand, a recent conversation with the manager >responsible for integrating the equivalent of AirFone into our next >generation airplane left me with the impression that there was quite a >big chunk of bandwidth required. One obvious solution would be an >onboard DS1 mux which performs upconversion at its output to an IF >frequency of the UHF set (most likely 70 MHz). I don't know whether >such a beast exists today, but I doubt that that's what is used in >most AirFone installations (i.e. one phone in the back of the plane). When I flew on the SAC airborne, we had UHF mux with 15 channels, and it was /old/ technology. While I agree that 400 would be overkill, I'd think standard telephone switch-sizing techniques would lower the anticipated service requirements down considerably. A designer might want to adjust for projected load-mix, such as a business shuttle vs vacation charters. Back in the old step-by-step telephone days, most installations only had line-finders for 10-15% of the phones in service. My guess is that for airfones, something less than that would be adequate. Ever had to wait for dialtone on your regular phone? It /does/ happen occasionally. <<<< insert standard disclaimer here >>>> riddle@hoss.unl.edu | University of Nebraska postmaster%inns@iugate.unomaha.edu | College of Law mike.riddle@f27.n285.z1.fidonet.org | Lincoln, Nebraska, USA
tnixon@uunet.uu.net (Toby Nixon) (01/11/91)
I just got back from a one-day trip to Washington DC. Both the trip up and the return were on one of Eastern's newly-upgraded 757s, with the huge first class cabin. Every seat in First Class has an Airfone imbedded right in the back of the seat immediately in front (the front row seats have the phone mounted on the bulkhead in front of them). As it turned out, we were required by an ATC computer outage to hold on the taxiway at National Airport for about 45 minutes. Being the nice husband that I am, I decided to call my wife and tell her that I'd be late for dinner. Quite a few other folks decided to place calls, too. Unlike the older Airfones with sort of a curved handset and little stubby antenna (cordless), these built-into-the-seat phones are rectanglar, and attach to the seatback by a cord that is obviously on a reel of some kind inside the seat. To release the phone from the seat, you press a credit card into a little vertical slot. All this does is depress a little mechanical hook, and the phone pops out. Several folks were initially confused by this, assuming that the slot in the seat was supposed to read their card, and got frustrated that the card wouldn't go all the way in. The flight attendants had clearly had to explain this to folks before, since they handled it nicely. The magnetic stripe reader is built into the side of the handset. Simply swipe the card through it. It DTMFs your card number to the control unit, apparently, since you can hear the tones in the background; you can go ahead and put the card back in your pocket (it doesn't retain the card like the older systems). I notice some folks having problems getting their cards to read, apparently because they were swiping them through too slowly. It doesn't say on the phone to do it FAST, but you need to. After reading your card and sending the info to the central controller, an awful digitized voice says "Thank you for using Airfone. Please wait for the dial tone." The first time I tried the call, I got the dial tone almost immediately; the second time (when a few other people were using phones), I had to wait a couple of minutes. When you get the dial tone, you punch in the number you're calling. The voice then says "Now processing your call; please wait." After a period of time (which also varied from a few seconds to a minute), the voice comes back on and reads you the number you dialed; I assume this happens while it is delivering the number to the PSTN, because almost immediately thereafter you start hearing ringbacks. On my first call, I got our answering machine. I used the telephone keypad to command the machine to play messages and a couple of other things, and it seemed to work fine (good news, since this means I could also use it to check voicemail at the office). I left a brief message, and hung up. This call was from the ground at National Airport. My second call was from the air, about 10 minutes outside of Atlanta airport. This time I got my wife on the phone. I had to TELL her that I was still on the plane; she told me that, except for a slight bit of background noise (wind noise, she said), the line was as clear as any payphone in the Atlanta airport. Anyway, that's my experience with the new Airfone system. It was very nice to be able to use my corporate AT&T Card instead of my American Express (as I'd had to do with Airfone before), because that way _I_ don't see the bill and _I_ don't have to account for it on an expense report! Nevertheless, it was also nice to read (on the instruction card) that they'd reduced the rates to $2 setup plus $2 per minute; really not bad at all. In article <15918@accuvax.nwu.edu>, ccplumb@spurge.uwaterloo.ca (Colin Plumb) writes: > All the airphones I've seen are all in one bank, so it makes more > sense for there not to be an instrument n+1 than for it to be where > someone can pick it up and not get a dial tone. If nothing else, the > physical "no more available" is more readily comprehensible to > passengers than bandwidth. This doesn't happen with the new system! You really do end up sitting there with the instrument on your ear, listening to dead silence. It would have been nice if there had been some repeated message to let you know that it hadn't gone dead. I did notice a couple of people give up in frustration; my guess was that they didn't realize they were having to condend with other passengers for circuits. It would be nice if the message explained the situation ( "all circuits now in use; please hold until a circuit is available" ). > (P.S. Do airphones check that you've put back the right phone before > releasing the credit card? It sounds like a great way to exchange a > stolen credit card for a good one. Insert piece of junk, remove > handset, replace in cradle holding gold card dext door. The getaway > offers problems, though.) The older Airfones would not release the card if you tried to put the wrong phone back in a cradle. Your card was locked in place to make sure you didn't walk off with the phone, but at the same time your card was protected because nobody else could get to it unless they returned the right handset. Of course, this isn't an issue with the new system. Toby Nixon, Principal Engineer | Voice +1-404-449-8791 Telex 151243420 Hayes Microcomputer Products Inc. | Fax +1-404-447-0178 CIS 70271,404 P.O. Box 105203 | UUCP uunet!hayes!tnixon AT&T !tnixon Atlanta, Georgia 30348 USA | Internet hayes!tnixon@uunet.uu.net
johnl@iecc.cambridge.ma.us (John R. Levine) (01/11/91)
In article <15918@accuvax.nwu.edu> you write: >But that's because customers demand conveniently placed instruments. >All the airphones I've seen are all in one bank, ... I've been on planes with one or two phones in the front and another in the back, but the real telephonic traffic jams occur on the BOS - LGA - DCA shuttles. On those planes, there is a phone in the back of every middle seat in every row (except presumably the last.) These phones are lightweight plastic handsets with a retracting cord. You release the phone from the seat by sticking your card into a slot that flips a simple mechanical latch, then run your card through a slot that runs the length of the handset. The reception is a little better than on the cordless model, but the handset is so light and crummy that it's hard to press the earpiece to your ear firmly enough to block out all of the background noise. Regards, John Levine, johnl@iecc.cambridge.ma.us, {spdcc|ima|world}!iecc!johnl