An abbreviation for direct dialling inward (also known as direct inward dialling). A system which allows an organization to have numerous individual phone numbers for each person or workstation in it's a PBX system that runs off a small block of dedicated phone number.
DDI allows the multiple lines to be connected to the PBX all at once without requiring each to have a physical line connectig to the Telco company.
A Dual River system supports this technology and can significantly reduce operating costs by reducing the number of phone lines you pay for, not the number of phones you use.
