Yamaha CL5 Reference Manual page 36

TO STEREO/MONO window (8ch)
Here you can control the on/off and pan/balance settings of the signal sent from input
channels to the STEREO (L/R) bus and MONO (C) bus, in groups of eight channels.
1
2
3
4
5
6
7
ST/MONO mode
1
Channel select button
Selects the channel. You can select multiple channels simultaneously.
2
Mode LEDs
The LED of the currently-selected mode will light.
3
MODE select button
For a MONO channel, the mode can be switched between ST/MONO and LCR.
For a STEREO channel, the mode can be switched between PAN and BALANCE.
4 ST/MONO buttons
These buttons are on/off switches for signals that are sent from each channel to the
STEREO bus/MONO bus when the MONO button is set to ST/MONO mode.
Σ clipping indicator
5
Lights to indicate a signal is clipping at some point in the channel.
LCR mode
35
Input channels
Reference Manual