in small quantities) and then bill per-minute or per number of channels which can be simultaneously in use. For the caller, these numbers can be assigned to locations which are a local call. Direct outward dialing The corresponding service to DID for outgoing calls from a PBX to the central office exchange is called direct outward dialing (DOD) or Direct Dial Central Office (DDCO). This service is often combined with DID service and allows direct dialing of global telephone numbers by every extension covered by the service without the assistance of an operator. The caller line identification (CLI) or caller-id of extensions for outgoing calls is often set to the extension DID number, but may be the organization's central switch board number. See also Dialed Number Identification Service Dial plan Voice over IP References Telephone exchanges