dlw@ucbtopaz.CC.Berkeley.ARPA (05/06/85)
Sorry if this has been discussed before - I don't read dcom religously.
I have just used a pair of Microcom "error correcting" 2400 baud async
dialup modems for a week and I'm hooked. The MNP protocol seems to take
care of all the line interference we have here, and the speed is addictive.
There are odd pauses even at times when the line is clean (errors are
noted by the TST light flashing) but this anomaly is far less annoying
than the constant garbage I was getting with 212a modems. (The interference
was so bad and so consistent with 212 that I set my flow control chars to DEL
and { just so I could work.) I did attempt to verify the salesperson's
claim that "even without error correction, the 2400 baud modulation
technique is less sensitive to line interference than 212a." I found this
to be not so. With error correction turned off, the SX/2400 was at least as
sensitive to our local interference. Furthermore the resulting garbage
was much less uniform than my 212a and thus my trick (above) was useless
making the situation totally intolerable.
I understand that Microcom has licensed the MNP protocol to other
manufacturers (Codex, Racal-Vadic, ...) so that we'll have a choice,
competition, etc. My congratulations to them for that! Also, public
networks such as Tymnet, Telenet, & Uninet offer MNP on their 2400
baud access indicating they think it'll catch on.
I'm convinced. "Don't leave $home without it." Any other views?
David Wasley
U C Berkeley
...!ucbvax!dlwsid@linus.UUCP (Sid Stuart) (05/09/85)
> >I'm convinced. "Don't leave $home without it." Any other views? > > David Wasley > U C Berkeley > ...!ucbvax!dlw You didn't mention that with the Microcoms internal buffering, the speed of the modem line and the speed of the rs-232 line are independent. I set my terminal up for 2400 baud on the serial port and I don't have to change it even when I call into a 1200 baud line and the modem autbauds... nice. One complaint I do have, though I don't know how much of a concern it is: When the modem is set to 2400 on the computer and a user dials in at 1200, it shifts to a citt standard for 1200 baud, and not bell 212. I haven't tested this with a bell 212 modem yet, so I don't know how much it affects the transmission quality. sid