DESC: The RS-232 serial cable connects into the Nexstar hand control or on some models, into the port on the drive base, and the other end connects into a computer.One end of the cable is a phone type jack, (RS-232) and the other end is a standard serial computer input. With CD ROM software this cable will enable your computer laptop or desktop to interface and control the telescope by pointing and clicking on sky maps shown on the computer monitor. With certain telescopes the cable allows downloading additional data from the Celestron website into the database of the Nexstar computer hand control.