The Avaya INDeX DPNSS cassette is similar to the Avaya INDeX DASS II cassette in that it provides the interface for a digital connection of up to 30 channels, although this time using the DPNSS protocol. DPNSS is a UK standard that has been widely adopted world wide. The protocol is designed to give feature transparency to the user between telephone systems (from the same or different manufacturers) in different geographical locations.