Feature group

A feature group, in North American telephone industry jargon, is most commonly used to designate various standard means of access by callers to competitive <a href="/facts/Long-distance_calling/gR0mtIeD">long-distance</a> services. 
They defined switching arrangements from <a href="/facts/Local_exchange_carrier/pc8QpYQM">local exchange carriers</a> central offices to <a href="/facts/Interexchange_carrier/zw2IppkH">interexchange carriers</a>. These arrangements were described in an official tariff[specify] of the <a href="/facts/National_Exchange_Carrier_Association/SoukNnQ3">National Exchange Carrier Association</a>, filed with the <a href="/facts/Federal_Communications_Commission/Ueghz8W0">Federal Communications Commission</a> (FCC).[when?]
While there are other feature groups for local access, the four common feature groups exist for access from the local subscriber to competitive <a href="/facts/Interexchange_carrier/zw2IppkH">long-distance carriers</a>:

Feature Group A
The original implementation, in which a user has to dial the local <a href="/facts/Telephone_number/Px4q5qFo">telephone number</a> of a provider's gateway, followed by (usually) a password, then the desired long-distance number. There is a different local access number in each local calling area. This requires no special capability at the local telephone company office as competing long-distance providers connected using standard local lines, which may or may not support <a href="/facts/Caller_ID/hh9DqEEj">caller ID</a>. If a carrier has no local presence, a <a href="/facts/Foreign_exchange_service_(telecommunications)/wFqjrzNy">foreign exchange</a> line is used to reach its nearest point of presence.<a class="footnote-ref" id="fnref:2" href="#fn:2">2</a> Once the standard means of accessing alternate long-distance carriers, local access numbers are now used primarily for low-cost prepaid calling cards as the calls may be made from any phone, at flat or local rates.
Feature Group B
Associated with 950-XXXX calling; instead of a local telephone number the user enters 950 and 4 additional digits which identify the long-distance carrier. Operation is similar to the local access numbers (feature group A) except that the 950-XXXX access number is the same in every community, <a href="/facts/North_American_Numbering_Plan/0QQ8v3ph">NANP-wide</a>.<a class="footnote-ref" id="fnref:3" href="#fn:3">3</a> Some exchanges send <a href="/facts/Automatic_number_identification/wjkfAgqo">the caller's number</a> automatically; where this service is not provided or not desired (calling card applications), the 950-XXXX number must be followed by a calling card number and the long-distance destination number. If ANI is provided, calls from the one subscribed line may be made as 950-XXXX and the long-distance destination. Largely deprecated by feature group D, but the 950 prefix and a list of carrier codes<a class="footnote-ref" id="fnref:4" href="#fn:4">4</a> remain reserved in all North American area codes, even in Canada where most providers went from feature group A directly to 1+ default carrier dialling and feature group D (101xxxx + destination) calling without ever using 950-XXXX as a primary means to access alternate long-distance carriers from home land lines.
Feature Group C
Rare, originally used by AT&T for operator-assisted coin phones since they allow the operator to keep control of the caller's telephone line until the transaction is completed.<a class="footnote-ref" id="fnref:5" href="#fn:5">5</a> As coin-handling for trunk calls is now automated within the phone (like a <a href="/facts/COCOT/6eI3r5H2">COCOT</a>, the current generation of coin phones operates self-contained without the central exchange providing coin-call support functions), group 'C' is largely obsolete.
Feature Group D
The current standard, requires the local switch support equal access by competing carriers at the trunk level; highest quality connection, and allows pre-selection of the <a href="/facts/Interexchange_carrier/zw2IppkH">interexchange carrier</a> by the end-user. This feature group permits two types of calls. If a user dials 1 + <a href="/facts/Area_code/jaryReDv">area code</a> + seven-digit number, the long-distance call is handled by a default carrier chosen by the user. Alternatively, a user dials 101 + four-digit carrier code + area code + seven-digit number, and the call is handled by the carrier specified by the carrier code.<a class="footnote-ref" id="fnref:6" href="#fn:6">6</a> The original batch of carrier codes began with 0, so this type of "dial around" service was typically marketed as dial-around 1010-xxx service. NANPA maintains separate lists of carrier codes for feature groups 'B' and 'D'<a class="footnote-ref" id="fnref:7" href="#fn:7">7</a> as not all long-distance providers support both standards.
These Feature Group alternatives allowed the LEC's end users to make <a href="/facts/Long-distance_calling/gR0mtIeD">long-distance calls</a> using the interexchange carrier's network, when non-stored program-controlled exchanges could not be modified to provide equal access. By the mid 1990s, Equal Access features in exchange software had rendered Feature Group D universally available in modern landline exchanges; the others are either used for calling card applications or are obsolete.

Feature group open-in-new

Feature group