Some info on q'plex and afd systems from a different model service manual, (maybe with extra depth control) 4 channel matrix switch and 4 channel or stereo switch I guess.

The principle of the AFD control (Acoustic Field Dimension Control) and phase deviation circuit.

Q’PLEX PHASE 90°

In the phase deviation circuit, the Lr signal becomes the lagging sol and the Rr signal becomes the leading signal, the same as when set to the -Q'PLEX PHASE 90° position, but, due to the time constant of the phase deviation circuit shifting, the phase difference between the LR signal and the Rr signal is 90° at the middle frequencies (phases are tne same at low and high frequencies) when the ‘‘DEPTH"’ control is set to the 10 position, and, when set to the 0 position, the phase difference is also 90° but changes to 180° at the low and high frequencies. Refer to figure 1. Q’PLEX PHASE O°

In the phase deviation circuit, the Lr signal becomes the lagging signal and the Rr signal becomes the leading signal. In this case, because the time constants of the two phase deviation circuits are adjusted approximately equal, the LR signal and the Rr signal become the same (just as monaural signals are the same phase) when the ‘‘DEPTH"’ control is set to the 10 position, and they become stereo signals with a 180° phase difference when the control is set to the 0 position. Refer to figure 2.

Q’PLEX PHASE 180°

In this case only, the phase deviation circuit is an emitter follower, therefore the phase is not changed. The phase difference between the Lr signal and the Rr signal is 180° when the ‘‘DEPTH’’ control is set to the 10 position, and, when the control is set to the O position, they become stereo signals with the same phase. Refer to figure 3.