JLCooper MCS3 MIDI - Manual (Page 5)

Connecting the MCS
3
Connect the supplied external power supply to the power jack
on the MCS
3
's captive cable.
In case a replacement supply is used, see to it that it has the
same rating as the original supply: The power supply's output
is rated at 9 volts DC, 500 mA, with a center positive 2.1 mm
plug.
Connect the MCS
3
's MIDI cables:
The connector labeled "To MIDI In" connects to the MIDI Input
of the machine your are controlling.
The connector labeled "To MIDI Out" connects to the MIDI
Output of the machine you are controlling.
5