ATA. Separating the ATA from the phone usually resolves the problem 9. Glossary VoIP Terms ANI Automatic Number Identification A telephone function that transmits the billing number of the incoming call (Caller ID, for example). MGCP Media Gateway Control Protocol A protocol for IP telephony that enables a caller with a PSTN phone number to locate the destination device and establish a session. BLI Busy Lamp Indicator A light or LED