CLASS - technical definition

Also known as custom calling services. A group of network-based services offered by local exchange carriers (LECs) through the public switched telephone network (PSTN). CLASS services include anonymous call rejection, automatic callback, calling name delivery, calling number delivery, calling number blocking, call waiting, distinctive ringing, call trace, ring again, selective call acceptance, selective call forwarding, selective call rejection, and selective call screening. For more detail, see also the preceding terms.