In the old days when using a PBX, you first needed to seize an outbound line before you could actually start dialing. After pressing the number, you would hear the dial tone from the trunk, or if something is wrong, a busy tone or just nothing. I remember when I started working for a company some long time ago, someone trained me how to make a phone call from my office phone. People got so much used to it, they get confused if they can just dial the number with a modern PBX. Even in the age when everybody has a cell phone.

Practically all VoIP phones can also give them a comfortable feeling by rendering a dial tone after that digit has been entered. Although completely useless, it seems to give users the comfort that they can now start dialing their number (which they can also without that key press). The problem with that is that every phone works differently, and it is practically impossible to serve all SIP-based VoIP phones in the provisioning process with those prefix numbers. Plus many phones are still set up manually, for example in the conference room.

For many years we told customers that they should just dial numbers as they dial with their cell phones. This is very simple, it is very easy to add numbers into the address book and we though over time everybody would be okay with it. However we still keep requests that customers are just not getting used to it. Even when dialing 911 people would dial 9911.

Anyway, we surrender. We have added a setting now that tells the PBX to strip a character from the dialed number. This should make those happy that don't understand that they can just dial the number. If people don't include the prefix and the number does not start with that number, then the number will still go through. It would not work in the case of 911 and a prefix of 9; but that can be still handled in the dial plan later if needed.