Originally posted by 10of40
....Just out of pure frustration, I toss in a US Robotics 28.8 ISA Winmodem and it works. Bloody 'ell.
.... the first thing a modem does when connecting is a 'handshake' .... by the looks of your descriptions all three of your 'errant' modems are 56.6 .... but the working one is only 28.8 ....

Sounds like the phone line to me - too much noise!

When modems connect on 'dodgy' lines ... they switch down speed until they find something acceptable , a 56.6 modem will keep this up until somewhere's in the "40s", then give up, if you know how you can in fact discover this yourself using AT commands....

The signal strength, the 'loudness', of the connection is much better at slower speeds so you usually get a connection with them....

I'd be taking a known working modem round there & testing it increasing the speed incrementally until I knew for sure....