OCU-DP CHNL UNIT-2 QCTL This product is used with the 3600 and 3600+ Mainstreet. The OCU-DP channel unit provides a special service data circuit for the 3600 Mainstreet. DDS I and II compatible. Error correction and secondary channel. Data rates of 2.4, 4.8, 9.6, 19.2, and 56kbs.