The Detector engineering control terminal can be used to communicate with one of the CCD controllers, including the autoguider CCD controllers. A limited number of CCD commands, used for assessing the performance of the CCDs and for taking test exposures when the VAX 4000 system computer is not available, are available to users and are documented in Section 8.3 of this manual. Rotary switch `B'' on the selection box between the engineering terminals must be set to the correct CCD controller.