buck@siswat.UUCP (A. Lester Buck) (07/19/89)
Here in Houston, U.S. Videotel and Southwestern Bell are offering a videotex service based on the French Minitel terminal, specifically the Telic Alcatel M 1B/US, made in France exclusively for U.S. Videotel. Currently, they have pumped about 20,000 terminals into the Houston market with various giveaways and free trials. U.S. Videotel estimates the critical mass for a successful service at about 35,000 installed terminals. Of course, the local hacker underground looks at these terminals and thinks how nice it would be to tap into this installed base but bypass the U.S. Videotel connection. The understanding is that these terminals, with built in modems, use v.23, which is something like 1200 baud in, 75 baud out. Could someone please tell me where I could get ahold of the v.23 standard, produced by CCITT I guess. Is there a U.S. distributor of these standards, or an address for CCITT in Europe? It seems that v.23 modems are quite expensive, around $800 and available only in Europe. Since the Minitel only costs something like $70-80, this is something of a problem. Assuming v.23 is basically 1200 baud in, 75 baud out, what are the possibilities of using standard 1200 baud modem chips? For example, on XT prototype cards, with some software glue for the startup protocol? As a last resort, wouldn't a software only solution work, as with the Commodore software serial port support? Thanks for any info, A. Lester Buck ...!texbell!moray!siswat!buck -- A. Lester Buck ...!texbell!moray!siswat!buck
johnro@microsoft.UUCP (John Rogers) (07/21/89)
In article <431@siswat.UUCP>, buck@siswat.UUCP (A. Lester Buck) writes: > [stuff about videotex terminals deleted] > > The understanding is that these terminals, with built in modems, use > v.23, which is something like 1200 baud in, 75 baud out. Could someone > please tell me where I could get ahold of the v.23 standard, produced > by CCITT I guess. Is there a U.S. distributor of these standards, or > an address for CCITT in Europe? Hi! According to my notes, you can get CCITT documents from any of the following: National Technical Information Service (NTIS) 5285 Port Royal Rd. Springfield VA 22161 main number: (703) 487-4600 sales desk: (703) 487-4650 General Secretariat Sales Service International Telecommunication Union (ITU) Place des Nations CH-1211 Geneva 20 Switzerland (22) 99 51 11 United Nations Book Store Room 32B U.N. General Assembly Building New York NY 10017 If you have any corrections to this list, or find an address for CCITT itself, please let me know. Thanks.
grr@cbmvax.UUCP (George Robbins) (07/21/89)
In article <431@siswat.UUCP> buck@siswat.UUCP (A. Lester Buck) writes: > > It seems that v.23 modems are quite expensive, around $800 and available > only in Europe. Since the Minitel only costs something like $70-80, this is > something of a problem. Assuming v.23 is basically 1200 baud in, 75 baud > out, what are the possibilities of using standard 1200 baud modem chips? > For example, on XT prototype cards, with some software glue for the startup > protocol? As a last resort, wouldn't a software only solution work, > as with the Commodore software serial port support? I think you'll find that the V.23 standard is much simpler than that used in the 212A style 1200 baud modems. It's a FSK half duplex scheme with a 75 baud reverse channel. This sort of thing can be handled by the simple modem chips used for 300 baud class modems, with no real handshaking is needed beyond a carrier detect for the originating modem. The closet us equivalent is the 108 series of datasets, though the frequencies are probably a bit different. Something like the AMD7911 "World Chip" FSK modem chip is pretty close the the state of the art "one chip does all" for this sort of thing, though you'll find plenty of alternatives needing more or less external analog circuitry. You also need some sort of serial interface capable of doing split transmit / recieve speeds, though a kludge of using two serial interfaces or using the uart for the receive end and bit bashing the 75 baud would be possible with a bit of cleverness. -- George Robbins - now working for, uucp: {uunet|pyramid|rutgers}!cbmvax!grr but no way officially representing arpa: cbmvax!grr@uunet.uu.net Commodore, Engineering Department fone: 215-431-9255 (only by moonlite)
emma@sbsvax.UUCP (Martin Emmerich) (07/26/89)
In article <431@siswat.UUCP>, buck@siswat.UUCP (A. Lester Buck) writes: > It seems that v.23 modems are quite expensive, around $800 and available > only in Europe. Since the Minitel only costs something like $70-80, this is > something of a problem. Assuming v.23 is basically 1200 baud in, 75 baud > out, what are the possibilities of using standard 1200 baud modem chips? I got a V.21, V.22, V.22bis, V.23 modem for less than three hundred dollars. Its a SmartLink2400A, from a taiwanese manufacturer. It receives the data with 121200 bps and sends it via the line by 75 bps. In the other V.23 channel it receives with 75 bps via the line and sends it to the PC with 1200. So I can use a normal terminal program at 1200/1200 baud. The list price for dealers would be $293 I was told. /\/> / ,--- / | Snail: Hangweg 9 / / _ __-/- o _ /-- __ __ _ __ o _ /_ | D-6601 Buebingen / /_/_(_/(_/(_(_/ ( /___//(_//(_(/_/(_(_(_/ ( | Voice: +(49)6805/8299 ---------------------------------------------------+------------------------- X.400: emma@sbsvax.informatik.uni-saarland.dbp.de | Z-Net: aniel@eiko.zer
cag@tigger.planet.bt.co.uk (Chris Green) (07/28/89)
> In article <431@siswat.UUCP>, buck@siswat.UUCP (A. Lester Buck) writes: >> It seems that v.23 modems are quite expensive, around $800 and available >> only in Europe. Since the Minitel only costs something like $70-80, this is >> something of a problem. Assuming v.23 is basically 1200 baud in, 75 baud >> out, what are the possibilities of using standard 1200 baud modem chips? > There certainly are reasonably priced v21, v22, v22b and v23 modems available, the one that immediately comes to mind is the (internal PC) Amstrad MC2400 at about 170 pounds sterling and a similar external model by Amstrad (SM2400 ?) at maybe 50 pounds more. These Amstrad modems (and most other recent ones) have internal buffering to allow the modem to PC link to run at 1200/1200 while the modem to modem link runs at 1200/75. It is possible to find v21/v23 only modems (rather old technology now) very cheaply indeed, mainly because Prestel and others gave them away with Prestel subscriptions. The main problem with these is that they are not buffered and thus need a PC with a split speed serial port. A standard IBM PC cannot do this so comms programs which can use these older modems have to have a software kludge to transmit at 75 while receiving at 1200. It can be done (I have a comms program called TranSend which does it very successfully and emulates Viewdata on a Hercules display) but it is not simple. You could probably get a V21/23 modem for about thirty pounds sterling and add about the same again for a program to handle the unbuffered modem and you could probably do Viewdata on a PC for about $100. Just need a friend in the U.K. to go shopping for you. If the requirement is a one off (or so) I wouldn't mind helping. By the way Prestel is now almost universally available at V22b so the requirement for V23 modems is steadily tailing off now, I suspect that it will soon be a thing of the past. Chris Green cag@planet.bt.co.uk