This circuit consists of a 20V supply powering a 1K ohm load. If the supply is shorted (switching to the 10 ohm load, the inductor will exhibit a spike in voltage, causing the op amp/comparator to saturate, outputting 15V. This is divided with the 1k and 2k resistors and fed to an SR latch. It will trigger the relay, disconnecting the source and protecting a hypothetical circuit from potential damage. The red LED will turn on to indicate the short.
