Why IP Phones have it own Dialplan?

Hi, If you see in Avaya you just configure the PBX, you don’t need to make changes to dialplan configurations like in Linksys/Cisco or any other Asterisk compatible IP Phones.

So, when you are configuring an extension you have to make the rules in extensions.conf OK
but then you have to move to the phone dialplan that looks like this


In my own opinion, I don’t know Why the IP Phones works this way :confused:

because unlike a Avaya / Mitel etc the handset on a sip system is a standalone device. some can be configured to do overlap dialing but most do enbloc the dialplan can be as simple as X. in many handsets meaning accepts any digits and dial when the “dial” button is pressed of the digit timeout is reached.