There are times when you want to test some programming in your 7330 to make sure it's doing what you want to, but you don't have the 7330 interfaced to a repeater yet. Or, the repeater is up at the site and the controller is on your bench. What's the best way to do that?
Many of us have built a radio port test box to use with the 7330. This gadget can be something very simple. My test box uses a pair of old powered computer speakers to hear the transmitter audio from two ports and toggle switches for the COR and CTCSS inputs to simulate a signal being received. If you can also find a DTMF keypad, you can generate tones into the receiver audio input for testing commands and macros.
Instead of toggle switches, you can use the COR and CTCSS Simulate Software Switches described on page 10-16 of the manual.
The radio port pinout is shown on page B-18.