This DC plug is required to power the Component Unit (CP-CC), Single Fan Unit (CP-SF) and Dual Fan Unit (CP-DF). One DC plug is included with each power supply and the Long Lead Y-Cable (PA-YC-LL). If using the Short Lead Y-Cable (PA-YC-SL) or Tri-Cable (PA-TC-SL) to power multiple units, you will need additional DC Plugs.