The CONKLIN Model 332 Issue 3 List 1 and List 2 All-Rate Office Channel Unit - Dataports (OCU-DP) are designed for use in Siemens 9004 A/B PCM channel banks for Digital Data System (DDS) or “DDS-like” services. OCU-DP units provide the interface between the 1.544 Mb/s bit stream of the system common equipment and the customer’s 4-wire local loop.