ETSI EN 300 267-6 English Printed Edition English PDF Integrated Services Digital Network (ISDN); Telephony 7 kHz, videotelephony, audiographic conference and videoconference teleservices; Digital Subscriber Signalling System No. one (DSS1) protocol; Part 6: Abstract Test Suite (ATS) and partial Protocol Implementation eXtra Information for Testing (PI

standard published 06/01/2000 by European Telecommunications Standards Institute