New in package One Telex "Sound Mate" NL-4S Neck loop with cable. New old stock unopened unused Plug it into Telex or other brand assistive listening receiver pack headphone jack (not included) "electro magnetically" transmits signal to Hearing aids that have built in T coil (most do) Allows user to keep their hearing aids in place and without having to take out or use earbuds or headphones. If you are not sure if your hearing aid has a T coil, ask your provider, or see if it works with telephones as most newer ones also have a built in coil in the handset. (some hearing aids have a hidden switch to turn it on or off) Good for churches, movie theaters, performing art theaters, walking tours or anywhere assistive listening systems are in place (or see our other listings if you need a system)