Audio cable tester

The Cable Tester v1.0 had some serious issues. That tester could detect non-connected cables/lines but it had problems recognizing miss-connected / switched cables. So I have made a plan for the newer version with the help of @davedarko's comment.

Check out and test online the new circuit: https://circuits.io/circuits/4643590

The new circuit needs a new box as well. But that is for another time.

The very fist version of the cable tester is very simple: four switches with four LEDs. When the cable connected you can switch on/off the buttons and the LEDs bright up if the line has connection. That seems simple and perfect. But ...

Circuit:

3d Printed Box:

And the final and working product:

Mismatched cables

But what does this circuit do when some cables are connected but in a wrong way? Sometimes it works just fine (left picture), but in other cases it makes false OK signs (right picture). So it is time to make a better version of the circuit.