This PCB provides the connections between all the daughter cards, plus the
main PCB (L122).
IC300 & IC301 (74HC244 buffers) take the clock signals (WClk, BClk & MClk)
from L115 & DSP WClk Out & DSPBClk Out from L156 and buffer them to the
ADC, DSP & DAC.
IC303 (74HC4040 divider) divides the MClk down to provide Clk PSU to sync
the switchers on L123.
L121AY – Connection board