Audicom Standard 3.5mm Jack Smartphone Headset Adapter Cable Converter to RJ9 Plug for Cisco Unified Office Telephone 7931G 7940 7941 7942 7971 and Plantronics MX10 Vista Modular Adapters(H35-CSB) Convert 3.5mm Smartphone plug to single 4P4C RJ9/RJ10 handset plug. NOT COMPATIBLE WITH IPHONE HEADSET. Still get great quality stereo sound from headset via this adapter Save money by buying a smartphone headset, or using your existing one with your phone's handset jack. ONLY COMPATIBLE WITH Cisco Unified IP Phones: 7931G 7940 7940G 7941 7941G 7942 7942G 7945 7945G 7960 7960G 7961 7961G 7962 7962G 7965 7965G 7970 7970G 7971 7971G 7975 7975G 6921 6941 6945 6961 7821 7841 7861 8811 8841 8851 8861 8941 8945 8961 9951 9971 and Plantronics Amplifier: M10 M12 M22 & MX10 Vista Modular Adapters BUY THE ITEM TODAY IF YOU HAVE ONE OF THE PHONE OR AMPLIFIER MODELS LISTED ABOVE. NOT COMAPTIBLE WITH CISCO SPA SERIES