If ‘HC’ CMOS is used, the inputs can withstand +/-20mA without latching-up (page 6 of this app note), so the 100k input resistor probably allows the encoder to be on a long wire – with all the ...

The USB-1616HS-BNC, a 1 Msamples/s, 16-bit USB data-acquisition device, provides 16 BNC differential analog inputs and handles synchronous and concurrent voltage inputs, waveform outputs, counter ...