ciaraldi@rochester.ARPA (Mike Ciaraldi) (03/09/87)
[I ain't afraid of no line-eater] This question seems to come up every few months, so now it's my turn. Some friends with a MicroVax running VMS need modems foor their incoming serial lines. They want 300/1200/2400 b.p.s. capability and the ability to occasionally dial out. If it matters, the modems would be connected to an Emulex multiplexer, which emulates a DH-11. They tried some Codex 2233 with bad results. First, they had to fiddle with the settings for quite a while to get the combination they needed. Once they were set up, the modems were very inconsistent. You culd dial in to the same modem 10 times in a row, and get a random mix of respones. One time it might work. The next time you would get a carrier from the Codex, but as soon as the calling modem sent its carrier the Codex would hang up. Another time the Codex would send its carrier, the sendingmodem would too, the line would stay connected indefinitley, but the Codex would never send "Carrier Detect" to the Vax. Also, once the modem stepped down to 300 baud it would not try to receive the next call at 2400 again; it would stay at 300 until manually reset. Then they tried some Hayes-compatible 2400-bad modems, but those had to be initiaized through software to make them auto-answer, not send messages, etc. This stuff has to be done, but cant be done with switches (the Hayes 2400 doesn't have switches like the 300 and 1200). So, that would have to be sent out the port when the system is powered up. We have several others coming in for evaluation, but would be interested in others' experiences. Mike Ciaraldi seismo!rochester!ciaraldi
mgrant@MIMSY.UMD.EDU.UUCP (03/09/87)
WARNING: Codex 2223 modems are trash! We had about 20 of them where I work, had the same bad results that have been described on this list, and returned them. We have do have some hayes 2400 baud modems. Yes they do need to be configured at some point. I wrote a script which just sends the correct AT commands to each of the modems when we boot the machine. Haven't had any trouble since. -Mike Grant
rab@well.UUCP (Bob Bickford) (03/10/87)
In a previous article Mike Ciaraldi writes: [skipping....] >Then they tried some Hayes-compatible 2400-bad modems, >but those had to be initiaized through software to make them >auto-answer, not send messages, etc. This stuff has to be done, >but cant be done with switches (the Hayes 2400 doesn't have >switches like the 300 and 1200). So, that would have to be sent out >the port when the system is powered up. Not quite true. The Hayes 2400 (at least, the ones I've worked with) has some EEPROM inside, and you can tell it to save it's current settings in that memory so it will come up in the right state if the power cycles. This is why they felt they could delete the DIP switches. Have a look at the manual; I don't recall the command but it should be easy to find. >seismo!rochester!ciaraldi -- Robert Bickford {hplabs, ucbvax, lll-lcc, ptsfa}!well!rab terrorist cryptography DES drugs cipher secret decode NSA CIA NRO IRS coke crack pot LSD russian missile atom nuclear assassinate libyan RSA
ciaraldi@rochester.UUCP (03/12/87)
In article <2742@well.UUCP> rab@well.UUCP (Bob Bickford) writes: >In a previous article Mike Ciaraldi writes: >>Then they tried some Hayes-compatible 2400-bad modems, >>but those had to be initiaized through software to make them >>auto-answer, not send messages, etc. This stuff has to be done, >>but cant be done with switches (the Hayes 2400 doesn't have >>switches like the 300 and 1200). So, that would have to be sent out >>the port when the system is powered up. > > Not quite true. The Hayes 2400 (at least, the ones I've >worked with) has some EEPROM inside, and you can tell it to >save it's current settings in that memory so it will come up >in the right state if the power cycles. This is why they felt >they could delete the DIP switches. Right you are! This morning I got hold of a real Hayes manual, not the clone one I had used (written in Japanese English). The command "AT&W" causes the current settings to be written to non-volatile memory, where they become the new default settings upon power-up or initialization. And the "AT&Dn" command can, among other things, make the modem reset whenever DTR goes low, which may be useful for modems that are both outgoing and incoming. And finally, Hayes even includes a couple of pages with recommendations for what settings to use for unattended dial-in operation. Oddly enough, they were the same ones we had worked out by wading through the manual. Thanks for the pointer, anyway. Mike Ciaraldi seismo!rochester!ciaraldi