1.Use the PC headset with most VOIP phones with an RJ9 / RJ10 / RJ22 headset socket (not compatible with RJ11). 2.Adapter cable with double 3.5 mm PC headset socket to RJ9 desk phone socket for , for 3. Because of current and impedance, the general computer headset is relatively small, compared to the effect of a professional telephone headset, there is a . 4. The pursuit of high-quality effects for professional products is recommended in order to make a . As the phone does not have uniform production standards, this product is for all phones of the (compatible with . 90% phone). 5. Convert two 3.5mm plugs to a single 4P4C RJ9 / RJ10 headset plug. With this cable you can make calls with your own headphones. Name: RJ9 adapter cable Color: Black Material: PVC Product size: 10x12x2mm Quantity: 2 pieces Package contents: 2 * adapter cable Only the above package content, other products are not included. Note: Light and different displays may cause the color of the item in the picture a little different from the real thing. The measurement allowed error is +/- 1-3cm.