MXtechnic RJ9 to 2 Port USB 3.5mm Female Headset Adapter Cable for Telephone (RCA Jack) Convert 3.5mm Audio plug to RJ9/RJ10 handset Jack Compatible with most IP phone headset jacks: Polycom, Nortel, Avaya, Aastra, ESI, NEC, RCA, Mitel, Lucent, Shoretel, Siemens, and more Get this headset adaptor then you can use your favorite computer headphone to chat on IP telephone Easy Setup, Plug and Play. Please note: It don't work with Avaya 9620C, Avaya 9608, Cisco 7942 ,Avaya 621xx. Connector A: 2* 3.5mm female ,Please note: There are 2 slots - one for mic works and one for headset works.Connector B: RJ9. Length:25cm