Relay-Version: version B 2.10 5/3/83; site utzoo.UUCP Posting-Version: version B 2.10.1 6/24/83; site fortune.UUCP Path: utzoo!linus!security!genrad!grkermit!masscomp!clyde!ihnp4!fortune!rpw3 From: rpw3@fortune.UUCP Newsgroups: net.dcom Subject: Re: Re: Signalman Mark XII - (nf) Message-ID: <1961@fortune.UUCP> Date: Wed, 14-Dec-83 04:02:39 EST Article-I.D.: fortune.1961 Posted: Wed Dec 14 04:02:39 1983 Date-Received: Fri, 16-Dec-83 01:45:41 EST Sender: notes@fortune.UUCP Organization: Fortune Systems, Redwood City, CA Lines: 27 #R:oliveb:-23800:fortune:3100001:000:992 fortune!rpw3 Dec 13 22:46:00 1983 Pure speculation, but... 1200 baud full-duplex "async" modems are not really async, since they use phase-coherent modulation. They are really synchronous modems with one-bit (or more) elastic buffers (FIFOs) for delaying your async characters into the synchronous slots. (This also permits them to accommodate a SMALL amount of difference in baud rate.) The early VADIC 1200 baud jobs even let you run the modem in true sync, if you wanted to (at least one stat/mux manufacturer ran the trunk line on them). My guess is that the modem you refer to uses some kind of SIO/UART/USART to receive the async for presenting to the modulator (though I have no idea why one might want to do that). Such chips cannot (directly) propagate without lots of pain from software diddling the status bits. Again, just a guess. Rob Warnock UUCP: {sri-unix,amd70,hpda,harpo,ihnp4,allegra}!fortune!rpw3 DDD: (415)595-8444 USPS: Fortune Systems Corp, 101 Twin Dolphins Drive, Redwood City, CA 94065