IBM Aptiva Handbook page 184

Table 15: Modem commands for DSVD
Code/Command Function
–SSE=n Enables/disables DSVD:
n=0 Disables DSVD.
n=1 Enables DSVD.
D Initiates transition from voice to DSVD.
H Hangs up the modem.
+VNH=n Used in conjunction with the ATH command for hook control:
n=0 The DCE disconnects the line (hangs up) when it does not detect a carrier.
n=2 The DCE remains off-hook when it detects no carrier. This allows the DTE to switch the DCE to another mode.
+VIT=n Sets the inactivity timer to n seconds, so the DTE cannot leave the DCE in an inaccessible state. The number of seconds can
be between 0 and 255.
168 Appendix C: Modem information