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Feature Group D (FG-D) is a term often used in the telecommunications industry to represent one of four types of access to long-distance service.
FG-D defines switching arrangements between local exchange carriers' central offices to interexchange carriers (long-distance telephone companies). This feature group allows a user to dial a long-distance telephone number and use a long-distance service provider depending upon the number dialled. A default long distance service provider can also exist on ths type of subscriber line.
FG-D belongs to the jargon used in the telephone industry for providing equal access between local exchange carriers' offices and interexchange carriers. The feature group categorizes the product manufactured by Telco companies based on services and features. The most commonly heard feature groups are FG-A, FG-B and FG-D; FG-C is used exclusively by AT&T for pay phones.
Feature Group D provides the highest quality connection and allows the end user to select the interexchange carrier. FG-D is sometimes known as equal access because it ensures that all the carriers are equally processed. The FG-D protocol specifies interconnection rules between a local exchange carrier and interexchange carrier.
The FG-D service routes calls with a carrier access code to the user’s carrier along with the caller’s number information. Because FG-D supports the transmission of caller information (Caller ID) it is used with 911 services.