OENORM EN 300138-4 V 1.4.3
Integrated Services Digital Network (ISDN) - Closed User Group (CUG) 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 (incl. Diskette!!!)