Custom local area signaling services

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Custom local area signaling services (CLASS) exploit the capability of the signaling network to pass the calling party’s number across the network. These call management services can be accessed by users from either dial pulse or dual tone multifrequency (DTMF) telephones. They permit CALLED party control over a set of services based on the CALLING party’s number. No special equipment is necessary on the customer’s premises, but a display device might be desirable to allow the user to identify the originator of incoming calls.

Nine CLASS services have been identified by Telcordia for use by business and residence customers. The intelligence necessary to support the services resides in the network. The following list shows some of the CLASS services.

  • Calling line identification
  • Distinctive ring
  • Selective call forwarding
  • Automatic callback
  • Automatic recall
  • Selective call waiting
  • Customer originated trace
  • Selective call acceptance
  • Selective call rejection

CLASS Examples

Four of the nine CLASS services defined by Telcordia are listed on the accompanying visual. These services are offered to customers served by central offices supported by the SS7 network.

These services are offered to both residential and business customers in bundled and unbundled offerings. For a set price per month, the service provider allows use of the services. Some services (e.g., automatic callback and call trace) could be offered for all subscribers and a per use charge would be billed to the customers.

It was once thought that the SS7 network would never generate revenue. With the deployment of CLASS call management features, service providers are realizing a revenue generation capability from the SS7 network.

CLASS Operation

All the CLASS services except automatic callback depend on passing the CALLING number from the originating to the terminating office. This requires that all the offices in question are equipped for SS7 access. The calling number is carried in the call setup message over the SS7 network.

Certain of the features require database query services in addition to the normal call setup messages. These are automatic callback, automatic recall, and user editing of the screening list(s) used for selective call forwarding, selective call waiting, and distinctive ringing.

All the intelligence necessary to support these services resides in the telephone switch and the SS7 network. If the user has the caller ID service, a display device is required at the customer premises on which to display the calling number.