ATA 23-51, Yoke Microphone Switch

The control yoke microphone switch has two functions. When the top side is pressed it activates the "PTT" or push-to-talk for the selected communications radio. When the bottom is pressed, the flight interphone is active.

Crews do not like having to key the interphone to have normal conversation in the cockpit. It was not uncommon to see a rubber band wrapped around the switch to keep it engaged.

My airline has modified the yoke microphone switch to lock itself in the interphone position. A small ball rides up and over a mount extension.
  
   A tool adjusts the height of the ball. To far up..... the switch won't lock. To far down..... and it blocks the switch from being used.
  
   As a note: When the switch is locked in the interphone position, the cockpit speaker is muted out. It is assumed the both crew members have their headsets on for communication.
 

The image of the switch above shows a switch that the ball and adjustment nut had fallen out of the switch rocker. It was being replaced at the time.

Locking switch part numbers.
  
  

Hi Mark thanks for all your helpful info about it, how "easy" could be to buy, adapt, and install these system in an aircraft?, the part number or how to find that  specific part is not clear.
I'm flying the 767, and I am also a mechanical engineer with some experience in maintenance, not in my actual company and neither certified, because it was in the Colombian Air Force 10 years ago.
I understand that there is a lot of paper work needed before making a modification to an airplane, but there are some few 767 of the fleet which was converted from PAX to Cargo, and after that conversion they became too noisy even afecting now the communications into the cockpit, especially on high power settings such as takeoff and approach, which are the most safety sensitive ones, but we as crew want to search for better solution, because we already tried to write it on the maintenance logbook, but the answer was that noise is just normal, but it is not, so now we are trying to find best solutions to this issue. 

Thanks in advance for your cooperation

Diego  C
767 Flight Crew

I was able to help a pilot from another small airline flying 767's in Alaska get the switches installed on their aircraft.

Contact your maintenance engineering department to see if something might be done for you.

As far as cockpit noise goes..... ANR (Automatic Noise Reduction) headsets work great.

Actually there is another solution, for us we dont have the toggle mod but we have small 3D printed buttons that can go on the audio select panel to hold the switch to interphone.

Do you have a picture?

true

Neat idea. Does the yoke mic switch override the interphone being locked down on the panel???

Yes the other PTT buttons will still work and able to use coma normally