Most modules require DC power which is supplied to the circuit board behind the module's panel.
Your system will need a power supply to convert the AC line voltages into the DC voltages needed by the modules. A DC cable harness takes power from the power supply and distributes it to the modules in your cabinet. You will also need one or more modules to control and interface to the AC line. A typical system would use a Q101 Control Module and a Q102 AC interface module, a power supply and a DC cable harness. The Q137 Module combines Q101 and Q102 functions in a single panel.