Polycom Vortex EF2241 Application Note page 16

Here's the good news. This bug only happens when a PC tries to Autoscan while
the 3Com modem is simultaneously connected to another Vortex and the
modem is on-hook. If you try to Autoscan while the modem is off-hook, this bug
does not occur. Also, because the bug doesn't happen while the modem is off-
hook, the bug will not occur if one tries to remotely call into the system.
Our recommendation is as follows: When setting up a system with a 3Com
modem, disconnect the modem while you are setting the system up. Once you
are finished, connect the 3Com modem and call into the system and verify that
the modem works. If you need to Autoscan the system in the future, disconnect
the 3Com modem.
We want to emphasize that this is not a bug with the Vortex. If the
modem enters into echo mode, the Vortex thinks that the echoed commands are
legitimate commands that must be processed. This is where the infinite loop is
generated.
16