jc_30120 - You say you are using U-verse VOIP to dial a security gate. How do you do that? Once the call is completed the VOIP system should not react to the buttons.

Or, You are using the same phone connected in parallel with the U-verse VOIP to control the security gate??

You need a way to open the VOIP path when you want to control the gate. But, then you would not have power to generate the tone.

The gate must have some instructions on setting this up. I would think that you would have the same problem with any phone service.