Reworking The Audio System
Here's the original Beech audio wiring behind the panel. NASA elected to keep their present audio system and to be honest, that was a good move. The factory audio system allowed transmitting and receiving on any radio for either side of the cockpit along with a nice built-in intercom; thus there really wasn't a reason to remove the factory audio system. We did have to change the front panel due to switch location changes and engraving. The wiring doesn't look like much at this point but Steve will clean it up prior to reinstalling it.
The second picture shows the toggle switches and the altitude pre-select. NASA elected to place the altitude pre-select in the center panel so both pilot and co-pilot could easily operate it. Each pilot can listen/talk on any radio they desire; this is a handy feature with a two person crew.