In the Soviet two-seater aircraft they do not have a hot microphone, you have to press a switch for communication between cabins and another for the radio. In the case of Soviet transport aircraft, there is a control box (SPU) that has a small switch that allows you to put the intercom on hot but without sensitivity, that is, all the noise and voice are transmitted, we used this a lot for the pre-flight check , inter-flight and post-flight, but later returned to the working position, which was, pressing a button to talk with other crew members, in the case of the Mi-8,17,24,35, the stick has 2 notches the first is the intercom between crews and the second is radio. In the case of the An-24, 26, 30 in the captain’s horn the button on the left is radio and the one on the right is intercom
I remember the first time I breathed oxygen through a mask it was with a KM-36, it has the microphone inside the mask cavity; I remember that I sat in an L-39, I connected the mask to the connector of the chair and I put on the mask and put on 100% oxygen, I remember feeling that tasty smell of fresh air with small hints of medical alcohol and that my lungs filled up completely with the positive pressure of the system, when I breathed I felt the valves of the same mask as they activated when exhaling and inhaling, after I took off the mask and began to breathe normally I felt like a vacuum, like I was short of air.
We also used 100% oxygen when we came to work after drinking, after a whole night without sleep, 10 min in 100% oxygen and ready for war. Of course, later you had to call the oxygen truck to refill.
In the case of the KM-32 and 34 mask, they use a microphone attached to their necks, called a laryngophone, which prevents breathing from being transmitted through the intercom or radio, but the voice quality is not very good.
