[hsflinux] RING not detected?

[Paul Miller]

USR 56K PCI Faxmodem (USR5660A)
Linuxant HSF hsfmodem_7.18.00.03full_i386.deb driver (free)
Kernel 2.6.10 + ACPI patches

In Linux, my modem does not respond to incoming calls.  It does not 
report RING or attempt to answer.  I have tried using the factory 
initialization string AT&F and it doesn't make any difference.

In Windows XP, my modem does report RING when receiving incoming 
calls.

What's wrong?