Feature Group B

With Feature Group B, calls are routed to the appropriate carriers via trunkside switching connections.  It is an alternative means for trunkside access to End Offices available for all traffic types. FG B is similar to FG D.  It can be provided with MF (Multi-Frequency for tone dialing), but not SS7.  

Since Feature Group B cannot be used for 1+ dialing, and it has no connection into the SS7 intelligence, it is not nearly as popular as Feature Group D.  However, it does support all types of traffic, including Calling Cards and Credit Card verification.

Feature Group B can be used to support Calling Card customers.  With Feature Group B trunks in the originating direction, the End Office switch recognizes a 3-digit calling card prefix and routes the call to a tandem where the number is translated and directed to the appropriate carrier.   End users must dial the IXC 3-digit number that identifies the carrier and the call is routed accordingly. The carrier then sends back a second dial tone that prompts the end user to enter a Personal Identification Number, or PIN number. If the number is valid, the carrier sends back a confirmation tone, and the end user may then dial the 10-digit long distance number.

Also, Feature Group B can provide terminating service LATA-wide and is used to access valid prefixes in the End Offices that access the tandem or to directly access End Offices. 

Where technically feasible, Feature Group B service can access time or weather announcement services, information services, and so forth. Typically, Feature Group B is provided through a tandem (tandem routing), however, Feature Group B can be provided through direct routing to an End Office in both directions.