Same as one before except simpler. This one will work the same except no led discriminator indicator and no 2 outputs. I have designed these 2 circuits they worked on a Pro2006. The circuit concerns me because it works off of straight voltage and not variable. How ever it is very simple and was the intent.
Any corrections welcome.
Here is the wave form they produce. As you can see it's a lot cleaner than the standard interface. Make sure your interface is made and connected properly. Connect a pair of head phones to the output of your interface check for audio. Sound Blaster can also make a good recordable oscilloscope.