The neck loop can be connected to guide systems, radio receivers or MP3 players. The connection is made via a 3.5 mm jack plug.Technical DataCable: 70 cmJack plug: 3.5 mmResistance: 5 ΩWeight: 35 gColor: BlackDocumentsDatasheet, english 1 page, 286 kByteVideosUnivox inductive listening systems - Instructions for laying copper foil for ring loops german, 3:36Univox Loop Designer 3.0 Webinar German german, 1:06:48Matching Products Univox IRR-1Infrared receiver for headphones/earphones or neckloops.