Avionics Bending: VHF/HF COM Radio Integration with X-Plane (Part 4)

Each crew member has three different ways of sending microphone input to the audio system.

1. There is a microphone attached to the headset worn by each crew member. 
2. A hand microphone is provided for the Pilot and First officer, and,
3. A microphone is installed in the oxygen mask

Each microphone is routed to the respective radio via the Mic Select switch on the audio panel. A radio will transmit when Push To Talk (PTT) switch is pressed. The pilot an First officer have 3 ways of keying the PTT:

1. The pilot and first officer yoke have a Push To Talk (PPT) switch on each yoke. The following two images show a typical Boeing 737 yoke with the PPT switch located on the forward facing side of the left hand grip.

B737 Yoke and PTT

B737 Yoke and PTT

2. Each crew station in the cockpit is also equipped with a hand microphone. The image below shows a typical Telex hand microphone as used on the L-1011 and many other aircraft type. The push button on the top of the hand mike has the same function as the PPT switch sown in example 1.

Hand Microphone PTT Switch 

3. The microphone can also be keyed with a small switch located directly on the audio selector panel. In most cases, this PPT switch would be used in conjunction with the Oxygen Mask microphone.

Audio Selector Panel PTT

For the simulator project, all three ways of keying the microphone results in a "transmit" setting on the flight simulator.