denber.wbst@XEROX.COM (03/06/87)
I need some help in a big way here. All I want to do is set up some modems so users can dial in to our MicroVax-II. We're running Micro-VMS and have a 16 port Emulex multiplexer board. It took the phone company 5 tries before we had our phone lines working (but that's another story). The first problem seems to be the modems. Has anyone ever used Codex 2233's? These are 2400 baud modems with about 59 million different options. Unfortunately, the options seem to have a habit of changing value by themselves seemingly at random. Specific problems include at various times randomly getting wedged such that only cycling power will reset them; failing to answer the phone even though set to autoanswer mode; going off-hook when no one is calling; answering the phone and then rudely hanging up on the caller; going into analog-loopback; and getting stuck at 300 baud (not resetting to 2400 for the next caller). On dialout, they lock up if they call a host running at 1200 baud (they drop down from 2400 to 1200 OK, but then refuse to send any data). After several days of floundering, we decided we didn't really want non-deterministic modems. We then tried a BytCom modem. This had the unfortunate property of not releasing the line when the caller hung up (yes the port is set to "hang"). Next we tried a "Mikon" modem (don't ask me where they come from - I just install them). This seems to work OK sometimes, although it also sometimes hangs up immediately after answering. Anyway, my questions are: what kind of modems do you use on your Vax for dial-in's? What lines does the Vax use to control them? (We're using DSR, CD, and DTR). I've noticed that our Vax normally holds DTR (pin 20) high on idle modem ports, but occasionally cycles it low for about a second, then brings it high again. Why does it do that? Could that explain the hang-up problem (like if someone is unfortunate enough to call in just when the Vax drops DTR, that would make the modem hang up)? Any and all help would be most appreciated. - Michel Denber.wbst@Xerox.COM
yerazuws@CSV.RPI.EDU.UUCP (03/09/87)
In article <870306-103725-1768@Xerox>, denber.wbst@XEROX.COM writes: > I need some help in a big way here. All I want to do is set up some > modems so users can dial in to our MicroVax-II. We're running Micro-VMS > and have a 16 port Emulex multiplexer board. It took the phone company > 5 tries before we had our phone lines working (but that's another > story). The first problem seems to be the modems. [many sob stories omitted - wsy] I have a MicroVAX II with a DHV-11 multiplexor board. Connected to this via a 25-line straight-thru cable is a Scholar 2400/1200/300 baud modem. It works fine except when the power glitches badly; the uVAX rides out the glitch just fine, but the modem sometimes decides to not answer the phone- ever. This has happened twice in three months. Power cycling restores the modem to sanity. The configuration on the modem line is /MODEM/HANGUP/AUTOBAUD. The DTR down/up is due to the uVAX thinking it saw something come from the modem (possibly a text message). VMS responds to the characters by printing the welcome banner and Username:. If it doesn't get a valid user/password pair in thirty seconds, it toggles DTR to tell the modem to drop the line. You can get the modem/uVAX into an infinite loop this way, (each one sending the other an error message, and getting an error message back). PBX data switches do it easily. This crashed our local data switch- IBX S40's can't deal with a DTR toggle every thirty seconds. The cure was to set the line NOMODEM on the data switch (NOT the dialup modem lines) Hope this helps. -Bill Yerazunis "People at the door, Daniel. Police, Daniel"
grr@cbmvax.cbm.UUCP (George Robbins) (03/10/87)
In article <KPETERSEN.12284849543.BABYL@SIMTEL20.ARPA> denber.wbst@XEROX.COM writes: >I need some help in a big way here. All I want to do is set up some >modems so users can dial in to our MicroVax-II. We're running Micro-VMS >and have a 16 port Emulex multiplexer board. It took the phone company >5 tries before we had our phone lines working (but that's another >story). The first problem seems to be the modems. Has anyone ever used >Codex 2233's? These are 2400 baud modems with about 59 million >different options. Unfortunately, the options seem to have a habit of >changing value by themselves seemingly at random. It is generally a mistake to use "smart modems" for what are strictly dial-in lines. There are just too many ways for them to get confused a lock out incoming calls. I would just use the basic dumb modems from a reputable manufacturer, or maybe a smart modem that has a physical switch/jumper to disable command mode. We have some dumb modems, some Racal Vadic VA212's which are smart but well behaved and a couple of USR Couriers. We use the Couriers for dial-in and uucp dial-out, and it seems that dialing out keeps them unwedged most of the time. -- George Robbins - now working for, uucp: {ihnp4|seismo|rutgers}!cbmvax!grr but no way officially representing arpa: cbmvax!grr@seismo.css.GOV Commodore, Engineering Department fone: 215-431-9255 (only by moonlite)
ciaraldi@rochester.UUCP (03/12/87)
In articlef <KPETERSEN.12285517636.BABYL@SIMTEL20.ARPA> yerazuws @CSV.RPI.EDU (Crah) writes: > The DTR down/up is due to the uVAX thinking it saw something >come from the modem (possibly a text message). VMS responds to the >characters by printing the welcome banner and Username:. >If it doesn't get a valid user/password pair in thirty seconds, >it toggles DTR to tell the modem to drop the line. > >You can get the modem/uVAX into an infinite loop this way, >(each one sending the other an error message, and getting an >error message back). PBX data switches do it easily. >This crashed our local data switch- IBX S40's can't deal with >a DTR toggle every thirty seconds. The cure was to set the >line NOMODEM on the data switch (NOT the dialup modem lines) > I was watching the modems at this installation today, and I don't think it is messages, for two reasons. All the modems are set up to be silent, i.e. not send any status messages to the vax. And, the pattern was too regular. The modem on the highest-numbered port would have its DTR ligt go off for about a second, then backk on. Within another second the next modem would have this happen, then the third modem and the final modem. About 30 seconds later the whole pattern would repeat. A few days before, whaen we hadn't managed to suppress all the messages, we would get "breakin attempt" messages on the system console when these spurious messages appeared, since VMS would assume it was someone wth a bad account/password combination. > > -Bill Yerazunis > "People at the door, Daniel. Police, Daniel" Once Dr. Manhattan finds his gluinos, we won't have these modem problems. (unintelligible to those who haven't been reading _The Watchmen_.) Mike Ciaraldi ciaraldi@rochester.edu or seismo!rochester!ciaraldi