peter@gen1.UUCP (Peter CAMILLERI) (05/28/87)
Often in spec sheets and product announcements for dat comm products
I notice that a disntinction between two types of modems. Regular and
Facsimile, and I can't help but notice that facs modems tend to be both
faster and cheaper than thier regular counterparts.
So my question is what is the difference between a regular modem and
a facs modem and can I use facs modems to create a cheap, high speed
private network?
Thanx for listening
--
Peter Camilleri UUCP: ...seismo!mnetor!yetti!gen1!peter
...utzoo!/ george@mnetor.UUCP (George Hart) (05/29/87)
In article <306@gen1.UUCP> peter@gen1.UUCP (Peter CAMILLERI) writes: > > Often in spec sheets and product announcements for dat comm products >I notice that a disntinction between two types of modems. Regular and >Facsimile, and I can't help but notice that facs modems tend to be both >faster and cheaper than thier regular counterparts. > > So my question is what is the difference between a regular modem and >a facs modem and can I use facs modems to create a cheap, high speed >private network? Turning it around, does this mean that regular modems cannot be used to connect to a fax machine? -- Regards, George Hart, Computer X Canada Ltd. UUCP: utzoo >!mnetor!george seismo BELL: (416)475-8980
gnu@hoptoad.UUCP (06/03/87)
In article <306@gen1.UUCP>, peter@gen1.UUCP (Peter CAMILLERI) writes: > So my question is what is the difference between a regular modem and > a facs modem and can I use facs modems to create a cheap, high speed > private network? Facsimile (usually abbreviated "fax") modems are just half duplex modems. For applications which can handle half duplex, they are fine. A friend of mine is selling 9600 baud fax modems on a PC-bus card, and has file transfer software and such for them. They are great if you want to send many kbytes in one direction before you get ANYTHING back from the other direction. It's like the difference between a Bell 202 modem and a Bell 212 modem. The 202 is 1200 baud, half duplex. You could get them used for $50 in about 1980. Even seven years later it's hard to get a Bell 212 (full duplex 1200 baud) modem for $50. The problem with general use is that these modems take anywhere from 1/4 second to a second to turn the line around and transmit in the other direction. This is rough on most applications, which assume instant turnaround. Even for old half-duplex terminals like the IBM 2741, a quarter second pause after you hit return was noticeable; the timesharing system I helped to manage tried to keep response into the 1/10th-second range except at peak hours. Note that most of the high speed "full duplex" 9600 baud modems are faking it. They use this kind of modem internally, but buffer the data and figure out when to turn the line around. So far none of them seem to have gotten it right, at least for interactive use. -- Copyright 1987 John Gilmore; you may redistribute only if your recipients may. (This is an effort to bend Stargate to work with Usenet, not against it.) {sun,ptsfa,lll-crg,ihnp4,ucbvax}!hoptoad!gnu gnu@ingres.berkeley.edu
hrs@homxb.UUCP (06/03/87)
> > > > So my question is what is the difference between a regular modem and > >a facs modem and can I use facs modems to create a cheap, high speed > >private network? > > Turning it around, does this mean that regular modems cannot be used > to connect to a fax machine? > -- > The modem in a fax machine is an integral part of the machime, at lest in G3 fax. The protocol starts trying to send at 9600, using V.29. For all other purposes besides fax, V.29 is considered a private line modem. Thus, the V.29 implementation in G3 fax is not considered to be a modem, but only an im[plementation of the modem protocol. If 9600 doesn't make it, the protocol falls back to 7200 V.29, and then to V.27ter 4800 and 2400. If you used a "regular" V.29 modem to connect to a fax, you would also have to implement the protocols. Thse are described in Recommendation T.30. Herman Silbiger ihnp4!homxb!hrs
gnu@hoptoad.UUCP (06/04/87)
In article <345@homxb.UUCP>, hrs@homxb.UUCP (H.SILBIGER) writes: > ...the V.29 implementation in G3 fax is not > considered to be a modem, but only an im[plementation of the modem > protocol. What's the difference between a modem and an implementation of a modem protocol? -- Copyright 1987 John Gilmore; you may redistribute only if your recipients may. (This is an effort to bend Stargate to work with Usenet, not against it.) {sun,ptsfa,lll-crg,ihnp4,ucbvax}!hoptoad!gnu gnu@ingres.berkeley.edu