The Headset Mate makes side by side training easy to achieve. A simple splitter with 4 pins one side and 2 pins the other. The trainer connects their handset to the 2 pin side and can listen but not talk. The other side has 4 pins connected which allows the user to speak and listen. Compact for storage when not in use RJ10 plug to twin RJ10 sockets (1x4P2C and the other 4P4C) for use with headsets with RJ10 4P4C plug.