The clock could show hours, minutes and seconds. To set the numbers, the board uses two 32bit shift register, the HV5122
, in series so the data out from one is the data in to the second. These drivers are high voltage and could handle up to 225V. One problem? The SPI port that this ICs are using to comunicate won't work well at logic level of 5V. So he had to create some voltage lever shifters with BJTs in order to send data to the chips. With these NPN transistors he was able to send 12V pulses to the chips.
On the back of the baord there is an 8bit microcontroller, a PIC16F886 that will control everything. By control I mean sending the signals to the drivers and by that show the time. THe board also has some push buttons so the time could be set very easy.