The Avaya INDeX DSLC provides the interface for up to 32 of Avaya INDeX's Digital Terminals (a range of four handsets). The full range is as follows; Avaya INDeX 2010, Avaya INDeX 2030, Avaya INDeX 2050 and Avaya INDeX 2060. These are described in detail in the Avaya INDeX Terminals section. There are four variants of the DSLC providing various quantities of extension circuits, this one being 16.

The Avaya INDeX DSLC16 cassette uses a proprietary 2B+D architecture (ISDN U interface) requiring only two wire standard twisted pair cabling to provide each user with a fully digital telephone which may be located up to 1000m from the Control Unit.