Flightcom 403 Intercom Muting…
I bought my RV-12 from original builder six years ago. My plane is an early SN with D180 instrumentation, SL40 Comm, and 403 Intercom.
Recently I have experimented with the Isolate/All switch on the intercom and discovered that radio reception is very much improved in the Isolate switch position. Isolate mutes the intercom so the comm radio does not “hear” cabin noise or passenger talking over radio reception. A little research shows that a set of jumpers can be added to the 25 pin connector on the 403 intercom which will give the comm radio full authority to mute the intercom when transmitting or receiving.
Pins 23, 24, and 25 can all be jumpered together to provide automatic muting. Flightcom ships the 403 with this jumper in place. It appears that Van’s did not replicate this Factory Shipped Muting Configuration when they made the wiring harness for the early legacy RV-12.
I’m in the process now of obtaining pins and D-sub crimping tool to make this change.
Below are screen shots of RV-12 electrical schematic and info from Flightcom Installation Manual.
What you discovered is an option to make this configuration in flight selectable. There are dip switches on the circuit board inside the intercom that permanently select these functions. This diagram shows how to add wiring to make them in flight selectable.
I had been in communication with technical support at Flightcom about muting the 403 intercom per above posts. Today I rec’d a phone call from a tech representative that is very familiar with the 403 intercom. He tells me there is no feature to allow the comm radio to automatically mute the intercom. The 403 does however, have a feature to “partial” mute the passenger mic when the comm radio is active. The technician told me all four DIP switches on the internal circuit board are shipped in the off position. If you turn switch #4 to “on” the intercom will partially mute when the comm radio is active. I’m going to schedule this next time I have the instrument bay opened up.
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