(S bits are unspecified) Figure 19.19 AU-4 pointer offset numbering. [From ITU-T Rec. G.709, Figure 3-1/G.709 (Ref. 7).] Negative justification opportunity (3 bytes) Positive justification opportunity (3 bytes) H1 H1 H1 H2 H2 H2 H3 H3 H3 85 86 86 86 521 521 125 us 522522 782782 H1 H1 H1 H2 H2 H2 H3 H3 H3 250 us Figure 19.20 AU-3 offset numbering. [From ITU-T Rec. G.709, Figure 3-2/G.709 (Ref. 7).] As shown in Figure 19.21, the AU-4 pointer value is a binary number with a range of 0-782, which indicates offset, in three-octet increments, between the pointer and the first octet of the VC-4 (see Figure 19.19). Figure 19.21 also indicates one additional valid point, the concatenation indication. This concatenation is given by the binary sequence 1001 in bit positions 1-4; bits 5 and 6 are unspecified, and there are ten 1s in bit ADVANCED BROADBAND DIGITAL TRANSPORT FORMATS NNNNSSID IDIDIDID 10-bit pointer value Negative Positive I Incremental bit justification justification D Decrement bit opportunity opportunity N New data flag bit New data flag Pointer value (bits 7-16) - Enabled "1001" - Normal range - Disabled "0110" AU-4, AU-3: 0-782 decimal TU-3: 0-764 decimal Negative justification - Invert 5 D-bits - Accept majority vote Concatentation indication values AU-n, TU-n type - 1001SS1111111111 (S bits are unspecified) AU-4, AU-3, TU-3 Null pointer indication (NPI) - 1001SS1111100000 (S bits are unspecified) Positive justification - Invert 5 I-bits - Accept majority vote Notes: 1. NPI value applies only to TU-3 pointers. 2. The pointer is set to all "1"s when an AIS occurs. Figure 19.21 AU-n/TU-3 pointer (H1, H2, H3) coding. [From ITU-T Rec. G.709, Figure 3-3/G.709 (Ref. 7).] positions 7-16. The AU-4 pointer is set to the concatenation indications for AU-4 con- catenation. There are three AU-3s in an AUG, where each AU-3 has its own associated H1, H2, and H3 octets. As detailed in Figure 19.20, the H octets are shown in sequence. The first H1, H2, H3 set refers to the first AU-3, the second set to the second AU-3, a