Connecting 2 machines over phone line

That would require a private phone line directly from home to office. The telco lines go to the telco office, not to your office (unless you work for the telco).

I believe you can connect two SDSL modems back-to-back, but not two ADSL modems.

Yes, it could work with various xDSL or EFM products, provided that you have a direct private line between the sites. You will probably want to look at the PHY types that support symmetric services (2BASE-TL, 10PASS-TS). Remember that both xDSL and EFM are master-slave systems that require different equipment at both ends of the line: one end will have the "central office" (CO) equipment, and the other end the "customer premises equipment" (CPE).

I am in the process of compiling a list of commercially available EFM equipment at

Regards,

Michael (remove filter from email address)