Xfox 4-pin RJ9 Call Center Hands-free Headset with Monaural Mic Noice Cancelling and Extra Cushions for Universal Avaya Nortel Nt Yealink Ge Emerson Office Desktop Telephone Direct connect over headset Microphone, compatible for the most telephones in call center. Just plug directly into your headset-ready telephone! You just simply plug this modular plug into the headset jack on your phone and it's ready to be used. Superior 150ohms speaker, to ensure the perfect voice quality. Noise proof microphone, to increase the voice clarity. NO Mute / Volume Control built in. Comfortable wear, compact appearance, human engineering design, Can be uninterruptible using.The headset clip can be stretched freely and comfortable wear. Kindly Notic:This is XFOX(A third party brand manufacturers) Universal Call Center headphone, if your telephone brand are Gaoke, Desay, Sanyo, Dex, Gaoxinqi Telephone, please use this convert adapter to connect the telephone(convert adapter is free). If you find this Mic Speaker can not work on your telephone, please contact us and tell us your telephone Brand and model befor you return, we will be pleased to answer any questions you may have, and we will be happy to assist you.