Master Fader of Summing Mixer ToolMix16 - Analog Summing Gear ToolMix
The picture shows 2 of the 16 inputs and the output section with master fader, fader on switch and pfl to output switch that routs the pfl master automatically to the main output, when a pfl switch is pressed.
Summing Mixer ToolMix16 

ToolMix16 detailed View Master Section