How to make a cable to transfer audio stream from phone to phone?

Question

Cables and wires

Good afternoon. There was an idea to transfer a conversation from phone to phone via an audio cable. What is this for me? One of the reasons is the recording of the conversation. In general, what was done by me: I took headphones with a microphone. I soldered the microphone, picked up and soldered the resistor. When you connect a headset, the phone detects it as having a microphone. And here's the rub. How to receive sound without a microphone if it will be transmitted from another phone? Or can it be done in a completely different way? Please share your ideas and opinions.

Answer 1

By the way, here is a link to the device, in principle, suitable for this habrahabr.ru/post/186456

Answer 2

Isn't it easier to turn on the recording of conversations in the phone: is it appropriate to install the application or tweak it in the engineering menu?