There is provided an adaptor for forming an electrical connection between a medical device having a first type of connector and an electrode having a second type of connector. The adaptor has a first connecting part shaped to cooperate with a corresponding connecting part on one of the medical device and the electrode so as to form a mechanical and electrical connection therebetween. The adaptor further has a second connecting part having a portion of magnetic or ferromagnetic material arranged to be magnetically attracted to a corresponding magnet or portion of ferromagnetic material included in a magnetic connector part on the other of the medical device and the electrode, so as to form a magnetic and electrical connection therebetween. The first connecting part is electrically connected to the second connecting part.