The Extension Unit is used in combination with a Control Unit (CCSD-CU or CCSD-CURD) to supply additional power to the CCS 1000 D Digital Discussion System. One or more Extension Units can be used to expand the CCS 1000 D Digital Discussion System up to 245 Discussion Devices. A single Extension Unit can provide power for up to 85 additional Discussion Devices (CCSD-DS or CCSD-DL).