8 7 6 5 4 3 2 1
1 H G F E D C B A
A Through-connection instruction indicator
0 no indication
1 through-connect in both directions
bits
B T9 timer instruction indicator
0 no indication
1 stop or do not start T9 timer
bits G-C Spare
bit
H Extension indicator
0 information continues through the next octet
1 last octet