Based on Alison Hine's advice about USB modems, I bought Entrega's USB
to Serial Converter, which allows me to run my serial modem from a USB
port and this seems to work very well. The documentation says that you
get all the benefits of a USB modem from your serial modem and I have
noticed a great improvement, although I still get disconnects
occasionally. If you already have a 56kbs serial modem this looks like a
cheaper alternative to buying a whole new USB modem and allows you to
run other serial devices though a USB port as well.
Cheers,
Paul