USRobotics V.34 - Manual (Page 142)

COURIER HIGH SPEED MODEMS
C-20 Alphabetical Command Summary
%T Enables the modem, when off hook, to detect the tone
frequencies of dialing modems. %T is meant primarily for use
with network applications, but may also be integrated into
certain software programs. For example, %T could be used in a
security program to identify incoming tone security codes.
To enable %T, type ATH1 to force the modem off hook.
Then type AT%T .
To return the modem to Command mode, press any key or
drop the computer's or terminal's DTR signal. The modem
responds OK.
%V=PW n Assign the password in account n in your Courier modem’s
security as your autopass password. See Appendix D.