Paradyne 2001 User Manual page 51

5) Jan also hears a
periodic beep to remind her
she is in data-only mode.
At any point she can tap
the hookswitch to return to
simultaneous audio and
data mode.
Jan might instead simply hang up her phone to transmit data at
high speed, and she might suggest to Chris that he hang up his
phone, too. This way she can perform other work while awaiting
Chris's return, and the completion of the file transfer. When
Chris gets back to the telephone and picks up the handset, a
ring signal is sent to Jan's DataPort 2001 alerting her that he is
ready to resume voice communication.
4) Chris hears alert tones
in his telephone handset
that mean Jan is in
data-only mode. Jan can
still hear Chris.