If you're talking about the equivalent of a person dialing on the telephone connected to the OBi's PHONE Port, the number dialed must match an SP2 DigitMap rule for the call to be sent out SP2. For example, if the SP2 DigitMap expects 7-digit numbers and you dial **2 1234567 123, then that dialed number won't qualify for being sent out SP2. **2 1234567 would.
If you dial **2 1234567 and then 123 after the call is to 1234567 is completed, the 123 DTMF tones will be sent out SP2.