10.59.4.3.2. Trunk Dial Tone 
In the US there is no specific external dial tone. Instead a pause
in the internal dial tone after a trunk access code has been dialed.
- To control the duration of this pause the following DTIM2 command is
used.
CHANGE-DTIM2:TYPEDH=GEN,PAUSDIAL=400; /* 400 = milliseconds between beeps*/
- In order to have the tone set to the correct timeslot use the following
commands.
CHANGE-ZAND:TYPE=TONES,CP=SECDIALT,SIU=0; /* To give silence during the pause */