AT&T MERLIN LEGEND System Reference Manual page 419

Features
Feature Interactions
Calling Restrictions
If a tip/ring equipment-user waits 15 seconds after hearing an outside dial tone,
the TTR is removed from the call. Once the TTR is removed, the user has
approximately nine seconds before the local telephone company disconnects
the call, and can override calling restrictions and dial undetected by the system.
System Programming
Change each individual line/trunk to rotary or touch-tone service.
LinesTrunks -> TT/LS Disc -> OutMode
Change each individual tie trunk to rotary or touch-tone service.
LinesTrunks -> TIE Lines -> Inmode or Outmode
2-370 Touch-Tone or Rotary Signaling