Direct Dial In (DDI) or Direct Inward Dialing (DID) means direct dialing (Dw) and is a feature ofprivate branch exch
offers the possibility to dial the extension directly via a single hunt group number in private branch exchanges with less than eight exchange lines.In the case of
extension number, thecall
number for the extension isappended to the number block of the hunt group number, which is the subscriber number. An extension number can also be provided for small telecommunications systems with only one basic access line. This possibility creates the prerequisite for the integration of data terminal equipment into desired network concepts or services
.Internet telephony, the SIP protocol with SIP-DDI (Direct Dial In) offers a direct dial-through option, which is carried out by the IP PBX. With this protocol, existing extension numbers can be ported.