What you see above is a master clock. It is the center of a system that can run an unlimited number of slave clocks, keeping them on-time thanks to its ability to synchronize with an atomic clock. [Brett Oliver] put together the project back in 2005 using digital logic chips, and no programmable microcontrollers. This includes everything from the binary decoders that drive the 7-segment displays, to the radio transceiver board that gathers the atomic clock data, to the various dividers that output 1 second, 2 second, 30 second, 1 minute, 1 hour, and 24 hour signal pulses. It’s a well document and fascinating read if you’re interested in digital logic clocks.