flinton@eagle.wesleyan.edu (05/15/91)
In article <3939.282a9a30@hayes.uucp>, tnixon@hayes.uucp writes: > > Well, it's not called "sanitary session shutdown" in V.32. It's > known as "GSTN Cleardown". What the modem does is initiate a > retrain request, but turn off all of the "rate bits" that indicate > the speeds at which it is willing to operate. This condition > (unwilling to operate at any speed) is defined as requesting the > call to be cleared. Most modems WILL properly hang up if they > RECEIVE such as cleardown sequence, but not all modems generate it > in response to a request for disconnection from their local DTE > (with DTR drop or ATH command). > Some years ago when I was using only 300 baud (ugh!) my ears could tell me that the reason my sessions with AT&T Mail ended without the gobbledy-gook, while sessions with my university mainframe ended with it, was simply this: AT&T Mail sent a long BREAK signal, during which my modem disconnected noiselessly, while the university simply dropped carrier, leaving my modem trying to interpret meaningless blobs of line noise until it decided there really wasn't any carrier left to demodulate. Not a cleardown sequence in the V.32 sense, but the same effect from my vantage point. [Toby: same thing apply at 1200? at 2400? -- seems to, though my ears fail me.] > > Toby Nixon, Principal Engineer | Voice +1-404-840-9200 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 > Fred E.J. Linton Wesleyan U. Math. Dept. 649 Sci. Tower Middletown, CT 06457 E-mail: <FLINTON@eagle.Wesleyan.EDU> or <fejlinton@{att|mci}mail.com> Tel.: + 1 203 776 2210 (home) or + 1 203 347 9411 x2249 (work)
tnixon@hayes.uucp (05/16/91)
In article <1991May14.231556.42791@eagle.wesleyan.edu>, flinton@eagle.wesleyan.edu writes: > Some years ago when I was using only 300 baud (ugh!) my ears could tell me > that the reason my sessions with AT&T Mail ended without the gobbledy-gook, > while sessions with my university mainframe ended with it, was simply this: > AT&T Mail sent a long BREAK signal, during which my modem disconnected > noiselessly, while the university simply dropped carrier, leaving my modem > trying to interpret meaningless blobs of line noise until it decided there > really wasn't any carrier left to demodulate. Not a cleardown sequence in > the V.32 sense, but the same effect from my vantage point. > > [Toby: same thing apply at 1200? at 2400? -- seems to, though my ears fail me.] Long-break disconnect is not required by any standard, although in Hayes modems it can be enabled at any speed. It only operates in non-error-control async mode (&Q0). If your modem receives a long break (1.6 seconds or more), it goes on-hook. If you drop DTR (&D2) or issue an ATH0 command, the modem sends 4 seconds of break before going on hook. Many non-error-control V.32 modems use this mechanism to try to eliminate garbage on disconnect -- but I still think using error control is the best way to solve the problem! -- Toby Nixon, Principal Engineer | Voice +1-404-840-9200 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