UNE-ETS 300188-4ED1

Integrated Services Digital Network (ISDN);Three-Party (3PTY) supplementary service;Digital Subscriber Signalling System No. one (DSS1) protocol;Part 4: Abstract Test Suite (ATS) and partial Protocol Implementation eXtra Information for Testing (PIXIT) proforma specification for the user (Endorsed by Asociación Espanola de Normalización in April of 2022.)