Autzoo.1657 net.periphs utzoo!henry Tue May 11 19:26:53 1982 Vadic 3451PA autodialing modem -- a review Basic rating: not bad. The 3451PA (this may not be the right part number, actually -- the box ours came in says 3451AD-P) is an autodialing version of the 3451P answer/originate triple modem. I strongly suspect, from inspection of the interior, that the difference is just new firmware. The price difference is trivial (a hundred bucks or so) and R-V will also upgrade existing 3451P's for some modest fee. The thing is a fully-functional 3451P triple modem. Talks 300 baud and both kinds of 1200, automatically recognizing what you are dialing in at. (There is a strapping option that puts a speed signal onto one of the RS232 lines so your system can autobaud if your terminal interface lets you see a reasonable number of modem lines -- DZs don't). It connects to the phone line via a standard garden-variety 4-wire modular jack. In the absence of nonstandard strappings, it supplies the usual modem control lines -- Ring Indicator means phone's ringing, Carrier Detect means there's carrier, Data Terminal Ready tells the modem it's ok to answer the phone (and dropping DTR tells the modem to hang up). NOTE: the documentation addendum that comes with the autodialing version claims that some of these lines are tied high to make strange terminals behave; fortunately, it appears to be lying -- the lines behave in the standard ways on our modem. The autodialer does pulse dialing only and is not very smart. There is no dial-tone detector or busy-signal detector. There is a character you can put in the number to say "pause 5 seconds here". Once the dialing is complete, the modem waits 20 seconds or so for carrier and then gives up. Nevertheless, this is enough (except for some of you Bell types who must have pulse dialing -- but you shouldn't need brand-X autodialers). The autodialer features are set up for use from a terminal, but it's not hard to use them from uucp. To get into autodialer mode, the phone must be on hook and you hit ESC CR. After that there is a simple ASCII dialogue, which fortunately does *not* include echoing, and which thus fits fairly well into uucp's stimulus-response login handling. Our uucp thinks our link to decvax is a hardwired line with a rather complex login sequence! Once the call has gone through, the autodialer says "ON LINE" and then you have a fully transparent data path -- you cannot accidentally kick the thing back into autodialer command mode. The thing has a couple of extra features like stored numbers that are not worth bothering with for computer use. Oh yes, and it has the nicest approach yet to dialout baud-rate control: it autobauds the ESC CR, and uses that as the speed for the call. There are two issues that need to be addressed to bring the thing up on your system. One is that you need a way to send characters to a line which has no carrier on it, so you can talk to the autodialer -- the standard drivers won't let the open() complete until carrier is there. If you are using the thing for dialout only, just wire the carrier line high; this is what we did as a temporary measure. The other issue is that the autodialer command mode can't take a burst of characters at full speed. I put a very simple change into our uucp conn.c so that a tilde (~) at the start of a response means "sleep 1 second before each character". This is crude but it works. We ordered this thing almost blind, in a desperate hurry to get a PO out the door before the money vanished, the afternoon before I went on vacation. We are very pleased with the way it turned out. Despite a number of interruptions and complications like a cross-wired modular adapter (existing hardware here, *not* from Racal-Vadic), our 3451PA autodialed decvax less than one working day after it arrived. ----------------------------------------------------------------- gopher://quux.org/ conversion by John Goerzen of http://communication.ucsd.edu/A-News/ This Usenet Oldnews Archive article may be copied and distributed freely, provided: 1. There is no money collected for the text(s) of the articles. 2. The following notice remains appended to each copy: The Usenet Oldnews Archive: Compilation Copyright (C) 1981, 1996 Bruce Jones, Henry Spencer, David Wiseman.