DISA stands for Direct Inward System Access and is a way to let inbound callers reach any internal extension. Once answered the system will play a message inviting the caller to enter the extension number to be connected to. The system also allows dialing outbound numbers, usually protected by a PIN code.
Checking “Allow outbound calls” will allow you to edit some more settings related to outbound calling:
The Welcome message is played to the calling party, usually asking to enter the extension to dial. If present, the PIN is requested to access this feature. It is highly advisable to set a
PIN when outbound calls are allowed.