Philips CDD522 Operating Instructions Manual page 25

In the Program Area (the actual user data area) the Q channel
carries info like Control, Address, Track No, Relative Time and
Absolute Time. In total 96 bits plus 2 SubCode Sync bits.
Subcode Frame: Q channel
(S0,S1,CONTROL,ADR,<:
pei 4 4
$0,S1: Syncbits (form the Syncbyte together with
other subcode channel Syncbits).
number of bits
Control: 00X0: 2 audio channels without pre-emphasis
10X0: 4 audio channels without pre-emphasis
00X1: 2 audio channels with pre-emphasis
10X1: 4 audio channels with pre-emphasis
01X0: Data track
XXOX: Digital copy prohibited
XX1X: Digital copy permitted
These bits can only change during a pause of
minimal 2 seconds or during Lead-in.
Address: Defines Q-channel Mode:
0001: Mode 1 Q-data, track/time information
0010: Mode 2 Q-data, disk unique catalogue
number
0011: Mode 3 Q-data, music-track unique
catalogue number
Since subcode is not subject to C1/C2
encoding, it uses its own Error Correction
scheme.
The different Q-data modes allow to interleave three types of data
in the Q-channel.
The Q-data Mode 1 must occupy in at least 9 out of 10
consecutive subcode frames. It is THE information
needed for search actions.
The Q-data Mode 2 must, if present, occupy at least 1
out of 100 consecutive subcode frames.
The Q-data Mode 3 must, if present, occupy at least 1
out of 100 consecutive subcode frames.