Telephone Pickup Coil with Sensitive Microphone

A sensitive microphone mounted on to a suction cup, connected to a lead terminated with a 3.5mm mono jack plug.
Stick the suction cup behind the earpiece on your telephone and it will allow you to listen to both sides of the conversation.
Plug the 3.5mm jack into a recording device to record the conversation or into a speaker to listen.

Record or amplify telephone conversations.