darrelj@Ucb-Vax.ARPA (01/03/85)
You have to be careful when buying 2400 bps modems (at least for other than
internal use where you can buy ALL of the modems) is that you get ones that
are likely to be compatible with what others have. I noticed that the DEC
modem in the compilation in V4 #140 is a Bell 201 standard modem, while some
of the others are CCITT V.24 (not sure about this number) which are quite
different.
Bell 201 is 2400 bps, but half-duplex over the switched network (you need a
4-wire leased line for full duplex). A venerable standard, but not
universally applicable because so many systems do not support half duplex
and syncronous operation.
Even being 2400 bps full duplex does not ensure interoperability (for
example of what can go wrong, look at 1200 bps full duplex modems where the
Vadic 3400 and Bell 212 protocols are utterly different implementations of
the same basic modulation scheme).
I don't know what standard will finally win out, but at least you know the
CCITT standards will work will most modems in Europe, and maybe here too.
Darrel J. Van Buer, PhD
System Development Corp.
2500 Colorado Ave
Santa Monica, CA 90406
(213)820-4111 x5449
...{allegra,burdvax,cbosgd,hplabs,ihnp4,orstcs,sdcsvax,ucla-cs,akgua}
!sdcrdcf!darrelj
VANBUER@USC-ECL.ARPA