This blog post will explain what direct inward dialing is. Direct inward dialing is a service offered by an Internet telephony service provider to route incoming calls to an extension on a PBX. The need for connecting a physical line into the PBX for each user is eliminated by using direct inward dialing service. DID numbers are purchased from an Internet telephony service provider and assigned to each extension on a PBX. When a DID number is called, the caller is connected to the extension assigned to that DID number. The need for an operator is eliminated because an extension in a PBX can be called via a DID number. The number of trunk lines required to make and receive phone calls can be reduced by using direct inward dialing service. A PBX can have a DID assigned to an extension which will eliminate the need for a phone menu or an operator. Employees can be reached directly by a customer. A business operating in a certain location can setup another phone number for another location to take advantage of that locations market. Using VoIP service eliminates the need to purchase hardware because calls happen within the telephone network. DIDS can be configured to forward incoming calls to another phone number. DIDS can be implemented with SIP trunking. SIP trunking makes using direct dialing inward service more scalable by allowing someone to add or remove SIP channels.