Feature Groups

Feature groups define the way groups of trunks and lines are provisioned and used by the IXC.  They allow IXC's to accept and deliver long-distance calls and other traffic across the switched network.  There are three primary feature groups in use today - Feature Groups A, B, and D.  They are often referred to in sharthand as FG A, FG B, and FG D.  FG C is no longer used.

Interexchange Carriers usually describe their trunk requirements to the LEC in very specific terms. Carriers also select the class of service they need from three basic classes known as Feature Groups A, B, and D. Each Feature Group is defined by the capabilities of its switching connection in any given End Office, and the services which that connection provides.  The technical characteristics, serving arrangements, and manner in which end users originate the calls may vary for each Feature Group.

To put it simply:

Feature Group A uses a lineside connection to the SWC switch

Feature Groups B and D use trunkside connections to the SWC switch.

The two types of Call Routing - facilities can be configured in one of two ways: Direct-Trunked Transport (DTT), and Tandem-Switched Transport (TST). DTT is always used to connect the SWC to an End Office or tandem. When trunks are tandem-routed, carriers are billed for Tandem-Switched Transport for the traffic between the tandem and its subtending End Offices.

The direct tranked transport if for dedicated access, such as a T1 from a PBX.  Anything that skips the tandem office and goes straight from the end office to the IXC  (DTT) is also known as "Direct routing".

Feature Group A - uses a lineside switching connection so that it is always direct routed from End Offices. This Feature Group is typically used by small IXC's (who is providing long-distance service for a rural town, for example) who need to provide end users an economical way to make long distance calls within their LATA.  FG A does not use trunks = only lines !!  When you use Feature Group A as an end user, you dial a seven-digit telephone number and hear a second dial tone. At that point you input a PIN plus the telephone number you want to call.

Feature Group B  - a trunkside switching connection available to all traffic types, and it has the advantage of a single nationwide 7-digit 950 number. This means that this carrier's end users can dial their Calling Card number for easy access to the carrier's services, enter their PIN, and then dial the 10-digit number they wish to call. In addition, merchants who need to call in credit card verifications are typical IXC customers who need Feature Group B.

Feature Group D - Feature Group D was established to offer Equal Access to competing carriers across LATA boundaries with 1+ dialing. This dialing pattern is attractive to end users because it eliminates the need to dial extra numbers to make a call.  It is the only Feature Group that offers 1+ dialing. This Feature Group furnishes trunkside access in the End Offices, and it can be Direct Routed to End Offices or tandems.  FG D is the most technically advanced Feature Group, and it was designed specifically to meet the requirements of Equal Access.This is by far the most popular Feature group, and in fact, it makes up over 90% of all feature groups.

Features of Feature Groups A

• Hunt Group Arrangements - arrangements on how to route calls when lines are busy (a specific order, or "hunt sequence" is set up)

• Custom Calling Features - 3-way calling, speed dialing, call forwarding, voice messaging, etc.

• Call Denial - screens terminating calls within a LATA to allow only 411, 611, 911, 800, 555-1212, and specific NXX's within the local exchange calling area 

• Service Code Denial - disallow termination of calls within a LATA to 0 and 555

• WATS - (Wide Area Telephone Service) - allows long distance calls to be placed by first dialing an 800 number

• Inter-LATA Toll Denial - same as call denial - but only Inter-LATA (long distance) and Calling Card calls are denied, and the caller is routed to a recorded announcement

Features of Feature Groups B and D

(note that Feature Group D is much more powerful - hence it's popularity)

• Supervisory Signaling - controls answering and disconnection of calls

• ANI - the ability to detect the number of the caller

• Flexible ANI - allows the ANI to be recorded in different ways

• Up to 7-digit Outpulsing - forwards 7 digits of the Calling Card access code to the IXC switch

• Alternate Traffic Routing - allows the IXC to have more than one route to the LEC end office, to be able to handle overflowing trunks

• WATS (Wide Area Telecommunications Service) - allows IXC's to provide 800 service toll-free to their users

• Service Class Routing - lets the IXC direct originating traffic to a specific trunk group dedicated to a certain class of service (i.e. Pay Phone calls, 800, 900, etc)

• International Carrier Option - forwards international calls to an IXC other than the one PIC'd to by the user.  This allows a customer to select a different carrier for his International calls

• SS7 Out of Band Signaling - separates signaling from the call.  It allows the IXC to offer "caller ID".  Of course, this is also offered by the LEC's for local calls.

• Operator Trunks (coin, non-coin, combined) - the ability to allow a combination of coin calls, Calling Card calls, Operator-assisted calls, and a combination of these from pay phones

• 64 Clear Channel Capability - the ability to use the entire 64 kbps of the DS0 channel for the call.  This requires out-of-band signaling, and therefore requires SS7

• Switch Net 56  (also called "Switched 56k") - switched calls with data (similar to 64k ISDN).  Used for data calls.  Also used for video (a series of 56k circuits are I-muxed together) - each 56k is one call and they all must be dialed separately - but once the connections are made, the paths are bonded together.

• Carrier Identification Parameter - requires SS7 - identifies the CIC (Carrier Identification Code) and thereby identifies who initiated the call