ched by the conversion Electrical interface specifications are usually measured during back to analog at the receive end. Measurements of this charac- equipment design and manufacture to ensure compatible intercon- terisitic can be made analog to analog (A-A), specified in CCITT nection between network elements at a Network Node Interface recommendations G.712 and G.713, or as a half channel measure- (NNI) and User Network Interface (UNI). Equipment normally Digital circuit test Digital Digital Digital switching transmission switching & multiplex performance & multiplex Primary Higher Coaxial cable Primary Higher multiplex, Transmission order optical fibre Transmission multiplex, order PBX or terminal microwave radio terminal PBX or multiplex multiplex switch (terrestrial & satellite) switch DSU Data Service Unit M Modem PBX Private Business Exchange Interface Interface Interface tests tests tests Figure 61.1 A telecommunications network 61/4 Telecommunication system measurements Table 61.1 Measurement and performance standards for digital transmission tests Measurement type International standards North American standards (CCITT) (ANSI/Bellcore) Interface PCM Codec G.712/713 (A-A) BSTR 43801 (TR-TSY-000499) measurements G.714 (A-D D-A) O.131-133 (measurement) Pulse shape G.703, G.975 (SDH) T1.403 Clock frequency T1.102(T1X1.4 revs.) TR-TSY-000499 Voltage/Impedance T1.105 (SONET) Coding T1X1.6 (Drafts) Framing G.704, G.706, G.708 TA-NWT-000253 (SONET) Jitter/Wander G.823 (European hierarchy) G.824 (N.A. hierarchy) G.995, G.782, G/783 (SDH) 0.171 (measurement) T1.102 T1.403 TR-TSY-000499 TA-NWT-000253 T1X1.4 (Drafts) conforms to the electrical characteristics specified in G.703, isolated pulse, typically preceded by 3 zeros to minimise inter-sym- T1.403, T1.102 or T1.105 (SONET), for the following parameters: bol interference (ISI). Either an isolated pulse test pattern is used, or the test receiver (e.g. an oscilloscope) must trigger on the right 1. Pulse shape, height, equality of negative/positive pulses. isola