ETSI EN 300 052-4 English Printed Edition English PDF Final draft Version 1.3.1Integrated Services Digital Network (ISDN); Digital Subscriber Signalling System No. one (DSS1) protocol; Multi Subscriber Number (MSN) supplementary service; Part 4: Abstract Test Suite (ATS) and partial Protocol Implementation eXtra Information for Testing (PIXIT) proforma

standard published 12/01/2001 by European Telecommunications Standards Institute