The FPD-104B-3 is a 4-channel frequency and period counter card for use in Curtiss-Wright’s EDAU/CDAU/WDAU-20XX series products. The card is capable of providing the current value of the period of a sinusoidal signal of engine fuel flow, or RPM sensors. Each card channel can accept an analog differential input, differential digital (RS-422) input, or single ended digital input. In addition each channel is configurable in the frequency counter mode, in the average period counter mode, or in the accumulator counter mode.