The sockets on the adapter are standard 3.5mm Stereo, which is what most disability related switches and products will have.
It is possible to change which button actions are connected to the sockets, but only at the time of manufacture. Four sockets is the practical maximum for this adaptation.
The adapter uses isolating relays and helps protect the electronics in the handset from the effects of anything that might be plugged in to the adapter sockets.
If in doubt, contact us through info@LEPMIS.co.uk.