Direct Outward Dialing (DOD) is a service of a local phone company (or local exchange carrier) that allows subscribers within a company's private branch exchange (PBX) system to connect to outside lines directly. Using DOD, a company can offer each person or workstation within the company the ability to dial numbers direct, without the need to go through an operator or dial other numbers first. DOD is often used together with Direct Inward Dialing (DID).
When DOD is used in a company with 100 workstations, for example, eight physical telephone lines (called trunk lines) might be rented from the telephone copmany. This would allow up to eight ongoing calls at a time; additional outbound call attempts would produce a busy signal until one of the calls completed. A DOD system can be used for fax, dial-up Internet, and voice mail, as well as for live voice connections. Compared to regular PBX service, DOD saves the cost of a switchboard operator, and calls go through faster.