Where is the phase switch on this schematic?

[Sadface]

Hi Guys,

I have a 40 year Miller & Kreisel Volkswoofer III that I need to do some minor repairs on.

I need to replace the gain pot and the phase switch.

Fairly straight forward but I can't find where in the schematic the phase switch is located.

It could be that I am blind however I cannot find a switch anywhere in this schematic.

 

[rayma]

Probably related to U2A, but the additional needed jumper is not shown.
See if JUMP4 has another jumper connected to it that is not on the schematic.