Relay-Version: version B 2.10 5/3/83; site utzoo.UUCP Posting-Version: version B 2.10.2 9/18/84; site brl-tgr.ARPA Path: utzoo!watmath!clyde!bonnie!akgua!gatech!seismo!brl-tgr!tgr!FONER%MIT-OZ@MIT-MC.ARPA From: FONER%MIT-OZ@MIT-MC.ARPA (Leonard N. Foner) Newsgroups: net.micro.cpm Subject: Hayes Test Pattern Message-ID: <231@brl-tgr.ARPA> Date: Mon, 2-Dec-85 19:03:09 EST Article-I.D.: brl-tgr.231 Posted: Mon Dec 2 19:03:09 1985 Date-Received: Thu, 5-Dec-85 06:32:29 EST Sender: news@brl-tgr.ARPA Lines: 20 I hesitate to mention this, because I'm sure someone's already said it and I haven't seen it yet. But... That UUUUU pattern you see is what happens when a modem which communicates in dibits (as does the Hayes) loses carrier. [Thus your 1200 bits-per-second modem is actually 600 baud, since each change of signal corresponds to a cartesian product of two one-bit quantities, (generally either phase and frequency or phase and amplitude---I don't recall which---each have two possible states, so you can combine them four ways to get a dibit) which means each change of signal can transmit two bits simultaneously. Anyway, 'nuff on that.] ASCII U is alternating ones and zeros, and the "no-carrier" state looks like the dibit for 01. Thus, you get a few UUU's and then the modem recognizes it has lost carrier. My VA3451 does that whenever the foreign system drops carrier on logout, for example. As for *why* one modem sees carrier dropped, I can't help you.