The IS-SCU homeruns to the IS-CCU to add eight door / sub stations and eight master stations to the system. Up to two IS-SCU's may be connected to the IS-CCU using three CAT-5e/6 cables. The unit can be rack mounted in an EIA standard rack (2U required) or wall mount using brackets. It is powered using an external 48V DC power supply, IS-PU-UL.