Note, the pictures of the old guide those persons using a mono plug, so take them only as a reference.
An old home phone handset.
A stereo plug 4-pin 3.5 mm or 2.5 mm (depending on your mobile).
Please note these wires are a bit 'special, I recommend tinned before soldering to the connector.
Solder the wires to the connector contacts that you will find the diagram shown.
Lock the strap clips into the connector, check the connections, check that there are no short circuits between the contacts, at which point you can close the connector.
The work is finished. Plug the earphones in place and you can call us comfortably without ears burn yourself during long phone calls.
The telephone cable may have the following colors:
These are the connection of some models, there are plenty. So I delegate to you to find your model here.
If you do not find your model, you need to disassemble an old headphones to control the connections.