This modular RJ9 connector is a 4 position, 4 conductor plug. It’s typically terminated on 4 conductor curly phone cable and used to connect a telephone handset to a telephone receiver.
This modular cord detangler has a
RJ9 male on one end and a RJ9 female on the other. It can rotate 360° and
is used on RJ9 handsets to keep the cord from tangling.