When putting together the CNC or other motion electronics, it's sometimes necessary to see if you have voltages in certain places. This tiny device will help with these little frustrations. Let me give you a scenario, you set up your CNC control software and the pins that will control certain axes, but you don't know if the software is talking to the pin. The 5V Tester LED can be connected to the actual pins at the back of the computer and show a light for high level and no light for low level. This device can also be used to troubleshoot electronic circuits.
If you need to determine is a part of a circuit has 5 volts, this is a little device that can do just that. This device will light an LED if there is 5v running through it from the red to the black lead. Stick this in your parallel port to see if you are getting the high or low voltage from your direction pin, put the leads to your limit switches to see if there is voltage across the wire. This tiny device comes complete with the wires soldered onto the board, a resister to limit the current to the LED and a green LED.