The BT Call Sign subscriber service is a way to have a separate number for your machine, it allows you to have at least two separate telephone numbers on one phone line. Each phone number has its own distinctive ringing pattern.

You can set up your machine so that it only responds to the second number.

When you set the BT Call Sign feature to ON, the receive mode is set to Manual automatically. Manual mode will not respond to incoming telephone calls, since the number you use for telephone calls will use the normal ring pattern. If you turn the feature off, your receive mode will remain on Manual.