This seems to be an elegant and simple solution to the problem of checking for continuity and shorts in a self made euro rack cable. You need only a few passive components:
It uses only passive components. You connect the DUT (device under test i.e. your self made cable) between SV2 and SV3 (SV1 is for powering the circuit). Given that all LEDs will form a long chain, their summed forward voltages must not exceed the supply’s voltage (he recommends to not use white or blue LEDs). According to the maker: “If there is a break in any of the conductors none of the LEDs will light. If there is a short between conductors the LED between those conductors will not light.”
It is show in detail here:
My version (leds were too bright to make a picture so I turned down the voltage and dimmed the light a bit):
Note, I extended the circuit a bit because I use 2x8 cables and connectors. So I used 15 leds which need about 15 * 1.95 V to light up.