piety@hplabs.UUCP (Bob Piety) (02/02/84)
It seems that I've heard something about the telephone company (ies) offereing a 56K bit digital service. Has anyone heard anything about it? Is it true? Available? When? Cost? Restrictions? Thanks in advance for your replies. Bob
smb@ulysses.UUCP (Steven Bellovin) (02/12/84)
From: piety@hplabs.UUCP (Bob Piety) Newsgroups: net.dcom Subject: 56Kbit telephone lines? Message-ID: <2174@hplabs.UUCP> Date: Thu, 2-Feb-84 14:43:40 EST It seems that I've heard something about the telephone company (ies) offereing a 56K bit digital service. Has anyone heard anything about it? Is it true? Available? When? Cost? Restrictions? Thanks in advance for your replies. Bob Yup, it's true. You're referring to CSDC (Circuit-Switched Digital Capa- bility); it's 56Kb *dial-up* synchronous (and can also run at 9.6Kb, I think). It will be available only at central offices that install some extra hardware and new software for their ESS. At the customer end, there's some box that takes the place of a modem. You can use the phone for voice or data calls; the data calls must be preceeded by a special prefix. As for availability -- to the best of my knowledge, the service has not yet been tarriffed. There are a few experimental installations in progress, in (I think) Georgia, Florida, and N.J. The real gotcha is that the service is syncronous. There are protocol converters available (for a few hundred dollars), but they don't go that fast. On the other hand, there hasn't been a market until now. I'm following this closely, because I'd like to have such a line to my house.... --Steve Bellovin AT&T Bell Laboratories P.S. I make no warranties as to the accuracy or reliability of the above information. It's my perception of reality, and has nothing to do with any official policies of my employer.
tim@minn-ua.UUCP (Tim Giebelhaus) (02/15/84)
I can't stand it anymore. I thought some one more knowlegable than me would reply. Anyway, 56 Kb can run several terminals at 9600 baud or better. The U of M's computer is not on campus, it is a few miles away. What some places in the U of M are doing is running a 56Kb line from the computer to the terminals. A mux makes it so several terminals can be run on the same line. The mux also takes care of the probelm of the sync. I have heard that the lines come in both varieties, though. It is about $1000 for installation of the line, and about $300 a month to rent the line. The Mux equipment is around $5000. It is a good deal considering all the modems and single lines you can do away with. A normal business phone is about $50 a month and how much to install. The best you can do on it is 1200 baud (normally). You can run 6 terminals at 9600 baud for about the same price. I have heard that you can get up to 32 9600 baud terminals on one 56Kb line. If you're like me, you did some quick math and said 32 terinals at 9600 baud? It works like this: not all the terminals are doing I/O at the same time. In fact, most the time, the line is just sitting idle waiting for you to type something. Even when you do type, you are not typing at 960 charicters per second. If everyone was getting graphics output at the same time, it would probably be slower. It would probably be a good idea to do some statistical analisis of your use to find out how many terimals you actually can use.