Now what to do with those letters? Well I like the feeling of plugging in a 6,3 mm / 1/4 inch audio jack just like in the old days:
And very conveniently the dumpster provided a nice little box with 18 large jacks on it. I recycled this front panel and put it in the box.
Here you can see the panel mounted on the side of the box. As you can see there are now letter under each of the jacks as well and 5 plugs inserted. The awake reader will see that the 5 letters are L A S E and R. That's right, you should put your Morse Code into this board. To make it a bit harder each plug has a number on it and an internal resistor that makes each plug unique by dividing the volatge in a unique ratio for each plug. You therefore have to put nr 1 in the first letter (L) and numer two for A and so on. The five jacks are then connected to 5 analog inputs and the analog value is right for only one of the plugs.
Here is the voltage on the letter R. It is 4.17 Volts after the voltage divider.
Resistors in the plugs. They are numbered as well when you put on the covering part of the contact.
As a final touch these plugs was mounted on the box with magnets. I drilled a slightly too small hole and hammered five neodymium magnets into these holes with a vinyl hammer. Quite neat!