The Nixie Clock uses the Make Controller’s Ethernet capabilities to go online and check what the time is, via a protocol called NTP ( ). Once it determines the current time, it uses the digital outs on the Make Controller to communicate with a pair of custom circuit boards that drives the nixies and updates the time.
Each custom board drives a pair of nixie tubes – they use a few ICs to allow 3 digital outputs from the Make controller to generate the 8 outputs needed for each pair of tubes. So, 4 nixie tubes (2 for hours, 2 for minutes) use 6 digital outputs from the Make controller. (Nixie tubes are old vacuum tube displays – each tube contains the digits 0 to 9. The Nixie Clock creates a clock with nixie tubes.)
4 digits Nixie Clock: [Link]