Help with setting a longer DTMF Signal

[RachelW]

Our building just installed a call box outside of our building and locked the doors to the general public. In order to get in the visitor must use the call box to call up to the company they are visiting. The person who answers the call box call then "buzzes" the person in by pressing #9 on the phone. Our problem is that our phones are not sending a long enough DTMF signal to trigger the door to open and someone has to physically go to the first floor and manually open the door for the guest to enter. I need to know how to have the tone of the button push last for longer than 1 second. Can anyone help me with doing this? We use the Yealink SIP-T22P model phone.

[Yealink Support]

Hello Rachel,
Sorry i am not very understand, when you need a longer DTMF tone? When you are pressing #9? Or after pressing #9?
About the door phone application, we suggest use our VP530, it's more convenient to open the door. You can just press Open Door button on VP530, and the door will be opened, and you can also see who is coming via the camera.
You can refer to attached instruction about our VP530 door phone feature.