Gives an overview of specific problems and requirements. Cross References:BS 4727:Part 2:Group 12BS 6667BS 7404:Part 1BS 7404:Part 2BS 7404:Part 3BS 7404:Part 4 BS 7404:Part 5BS 7494:Part 1IEC 353IEC 481IEC 495IEC 663IEC 834-2IEC 870-6IEC 1000ANSI/IEEE STD 367IEEE P 565/D3 5-27-77CCIR, XVIth Plenary Assembly, 1986, Volume IX-Part 1 CCIR, XVIth Plenary Assembly, 1986, Volume VIII-Parts 1-3 CCITT Blue BookCCITT Recommendations X.400 - X.420
