WHAT IS DID - DIRECT INWARD DIALING?
DID - Direct Inward Dialing is a feature offered by telephone companies for use with their customers' PBX system, whereby the telephone company allocates a range of numbers associated with one or more phone lines.
Its purpose is to allow a company to assign a personal number to each employee, without requiring a separate phone line for each. That way, telephony traffic can be split up and managed more easily.
DID requires that you purchase an T-1 or Digital line and ask the telephone company to assign a range of numbers. You then need DID capable equipment at your premises which consists of BRI, E1 or T1 cards or gateways.