Custom Local Area Signaling Services (CLASS)
As the Local Exchange Carriers gradually migrate to SS7 signaling, PSTN users are provided with sets of features. One such feature set is known as CLASS (Custom Local Area Signaling Services), a Service Mark of Bell Communications Research (BELLCORE) and Bell Atlantic. These are usually called something else wthin the LEC (e.g. GTE’s “SmartCall” services in the Tampa, Florida area, etc.). A brief description of these features is included in the table below. Intra-LATA availability of these features is LEC dependent, while Inter-LATA availability depends upon both the IC and the LEC:
Note 1: Incoming Caller Line ID (ICLID) services CAN BE PROVIDED OVER STANDARD ANALOG 2-WIRE LOOPS. The End-Office switch transmits the ICLID information through "modem bursts" between the first and second ringing cycles. The user's POT (Point Of Termination) must have a special phone or adapter box that provides the decode/display functions. If the user picks up the handset during the first ring cycle, there is a possibility that the ICLID information may not be received properly! When calls are placed from PBX users, the Calling Party information transmitted throughout the PSTN usually includes only the MAIN PBX NUMBER (e.g. the PSTN does not provide information regarding the PBX extension). ICLID is sometimes equated with Directory Number (DN), and Calling Party Number (CPN) terms. ICLID is NOT THE SAME as AUTOMATIC NUMBER IDENTIFICATION (ANI), since ANI represents a BILLING NUMBER (BN). Note 2: Incoming Caller Line ID (ICLID) and Customer-Originated Trace (COT) CAN BE SUPPORTED in Inter-LATA environments if both the LECs and the selected ICs utilize compatible SS7 interconnectivity.