Help with selecting site dial-in modems.
bshafer
years old) in the next few months and I am seeking information and
others' experiences with dial-in modems.
Our criteria are reliability, reasonable price, maintainability and good
vendor support.
We would like a rack mountable 2400 (V.22 bis, V.22 A or B), 1200
(Bell 212A) and 300 (Bell 103) compatible modem. We would like
it to support originate/answer and autodial (Hayes protocol is ok but not
essential). They will be placed on our MICOM data switch and pooled for
both incoming and outgoing calls to/from our VMS and Un*x VAXen.
We need 24 to begin with and would be interested in selling the standalone
compliment(s) in our Computer Store.
The issue of error correction is unclear to me. Not the need so much as
the how. Almost everyone is now selling modems with various levels of MNP.
My question is why choose a proprietary protocol over something
like X.25? (Yes somebody does make an X.25 2400 baud dial modem - I think
it is General Datacomm). It also occurs to me that these protocols are
more than likely burned into PROMs. If that is the case, are any of the
vendors suggesting that if something other than the protocol they sell
becomes the standard that they will have a cheap upgrade path?
I would appreciate any advice and I give my thanks in advance. If I
get enough responses I will post a summary to the network.
--
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Bob Shafer | ... {hplabs, seismo}!hao--\
CaIR | ... ucbvax!nbires----------> !udenva!bshafer
University of Denver | ... {boulder, cisden}-----/
Denver, Colorado 80208 | Phone: (303)871-2091
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bshafer
ber...@clio.uiuc.arpa
I strongly recommend NEC modems.
1. Educational institutions get a hefty discount.
2. They're industrial grade modems made to Western Electric
standards. The filters are 10db better than the cheap plastic
hobby modems (Hayes, US Robotics, etc.). They meet all
Bell specifications, although there's a switch to let the modem
meet sloppier tolerances (for full compatibility with the
cheap plastic modems too)
3. They're available in rack mount. In fact, some models plug
right into a standard Western Electric modem card rack.
4. Hayes command set and MNP error correction are available if
you insist. I prefer the NEC proprietary autodialing menu.
We have a couple dozen NEC modems of various vintage and model
in the field and on the computer. They all perform admirably.
Long distance file transfers are error free, and we haven't had a
single modem fail yet. They're warranted for 5 years.
Contrast this to reports favoring (!) US Robotics modems that have
appeared over the net. One report favoring the USR product boasted
that they "worked fine", although he pointed out that four out of
twelve were DOA! Another report claimed "only two or three errors
in a two hour long distance file transfer". Yuck!
The NEC modems have a variety of self-test features.
Art Zemon
I have had excellent results using various Racal Vadic
modems over the last five years. Right now I have eight
rack mounted VA4224 modems (2400/1200/300 baud with MNP) in
the computer room. In users' homes are a variety of US
Robotics, Prometheus, and Racal Vadic modems. By far the
most reliable units are the RVs. My favorite, and the only
type I now buy for home use, is the Racal Vadic 2400PA. It
is essentially a standalone version of the 4224 with some
additional "user friendly" features like a dialing
directory and EEPROM configuration instead of DIP switches.
I did a bunch of side-by-side when I decided to move to
2400 baud modems and found that the Racal Vadic really did
get fewer line errors than the USR Courier (RV running
without MNP for this test) and the Hayes 2400 and all the
others that I tested. I did not try a NEC so I cannot give
you a direct comparison.
In closing here is my general advice for buying modems and
stereos: Spend a lot of money. Dollars seems to be
directly proportional to the quality of the analog
circuitry. (Of course you also need to find reputable
dealers with roughly equivalent prices for this to work.)
Feel free to call me if you want to talk about this stuff.
(714)966-2344.
--
-- Art Zemon
FileNet Corporation
Costa Mesa, California
...! {decvax, ihnp4, ucbvax} !trwrb!felix!zemon