I am currently looking into the feasibility of a continuity tester for a 16 channel audio snake system that we use. Here is the general idea that I have. The pins at the female end of the snake would be connected to one pin of a shift register (to maintain isolation for each pin). The pins at the male end of the snake would be connected to a 4051 multiplexer chip. The idea is to step through each pin, set the shift register output high, and then check to see if the corresponding multiplexer pin has voltage.
Here is a quick drawing I did for 8 pins to help illustrate my idea:
Is checking 54 pins this way a good idea?
If so would isolation between the snake and arduino be a good idea?