This clock is unique because not only it shows seconds but even tenth of a second. It is a seven-digit clock. It is also called the atomic clock. This unit has three frequency captures. 5,10 and 15Mhz. In some areas depending on where you live, the antenna that is included can pick up a signal and automatically show correct time display on its own. As I seen in some videos. But in some cases, most likely, this unit will require an external type. (Not Included.) This clock has two DIP switches on the underside that are preset. According to your time zone you're in, the first four switches will need to be reset. This clock is fully functional and manually tested. This unit is New (Not Used). The body cabinet is in Good condition. Also a 20ft. power cable 12VDC, an extension cable, 33K ohm test resistor, antenna cap, original manual, schematics, and pictorial are included. Thanks for looking.