Morse Decode With An Old Android Smartphone

This describes an experiment using a telephone receiver insert as a microphone feeding a smartphone running the Morse Expert app.
The Morse Expert app uses the same algorithms as CW Skimmer, the link to the Morse Expert website follows:- https://ve3nea.github.io/MorseExpert/
The website mentions that a direct connection to the radio is desirable to avoid echo distorting the waveform but this is not always easy and you can get earth loops,etc when equipment is connected directly. I decided to try using a normal telephone receiver insert as a microphone as they are mid impedance (300 ohm) and have a flat frequency response from 300-3400 Hz, they can also take quite high volume without distortion. The insert can be put very close to the receiver speaker and the Android phone put in a convenient place for the operator. The insert needs to be on some foam to prevent sound transfer from the surface the insert is on.
A video of the experiment is on this link:- https://www.youtube.com/watch?v=-tJ_IjwQlRM
The microphone connection for the Android is with a 3.5mm 4 pin male jack plug. The connections are sleeve and ring 2.
Here is a pic of the final set-up in use, I am pleased with the results which are much better than using the phone with the internal mic.
Derek Stewart G4HSY