How does the “AUTO TAKE” feature on the Panasonic WJ-MX12 work?
According to the Instruction Manual for the WJ-MX12 from Panasonic, the "AUTO TAKE" feature allows "A WIPE MIX EFFECT mode" to be "operated automatically without changing the MIX/WIPE lever."

This is from pp. 2 of the manual that you can read here:

http://tda.panasonic-europe-service.com/docs/2z4fd648faz3z1f340z656ez706466z35z6265ac2843a7c8785ba2cc5185b68bc80d0f9dea/ttips/Visual/Mixers_Edit_Controllers/WJ/MX12/727808/BMX12.pdf

On pp. 16 item 4 of the same manual there are more details