Doepfer LMK2+ Midi Master Keyboard (new version with USB) - Manual (Page 11)

LMK2+/USB User's Guide Page 11
Appendix B: Pin Assignment of the Jack Sockets
"high"
end
"low"
end
2...10k linear
Foot Control
Foot Switch
Foot Switch 2 (Sostenuto)
Foot Switch 1 (Sustain)
1 2
Power Supply
1 = +7...12V DC
2 = GND