User-to-user indicators
8 7 6 5 4 3 2 1
1 H G F E D C B A
A Type
0 request
1 response
If bit A equals 0 (request):
bits
C B Service 1
0 0 no information
0 1 spare
1 0 request, not essential
1 1 request, essential
bits
E D Service 2
0 0 no information
0 1 spare
1 0 request, not essential
1 1 request, essential
bits
G F Service 3
0 0 no information
0 1 spare
1 0 request, not essential
1 1 request, essential
bit
H Spare
0
If bit A equals 1 (response):
bits
C B Service 1
0 0 no information
0 1 not provided
1 0 provided
1 1 spare
bits
E D Service 2
0 0 no information
0 1 not provided
1 0 provided
1 1 spare
bits
G F Service 3
0 0 no information
0 1 not provided
1 0 provided
1 1 spare
bit
H Network discard indicator
0 no information
1 user-to-user information discarded by the network