The Plantronics APN-91 EHS cord works on the NEC phone models DT330, DT430, DT700, DT730, DT750, DT830, DT830G and allows for electronic, invisible remote call answer/end capability from the following Plantronics wireless headset models: CS500 Series (CS540, CS530, CS510, CS520), Voyager Legend CS, Savi W700 Series (W710, W720, W730, W740, W745). If you have one of the older wireless headset models (CS50, CS55, etc.), then this EHS cord will not work for you. Instead you would need the HL10 automatic handset lifter. Please feel free to call with any questions.