OvisLink Dual Ear Call Center Headset model OVHSM384-SYN is designed to be compatible with AT & T Syn248 Business phone SB35025 and SB35031. It comes with a quick disconnect cord that connect the headset directly to the AT & T phone Xblue IP7g, X3030, X4040 IP Phone, Xblue X25, X50 phone sets' headset jack, no amplifier is needed. Headset volume is controlled by the volume buttons on the phone's keypad. To activate or deactivate the headset connected with the phone, simply press the headset button on the telephone keypad. This OvisLink Call Center headset services with solid, crystal clear voice quality when use with Syn248 Business phones. The OVHSM384-SYN is a corded call center headset with Over-the-Head design. It has two earpieces to cover both ears, helps user more focus on phone conversation. The Headsets' key features include Acoustic Shock Protection (when the electric overcharge signal of 6v or above comes to the receiver, it will be cut off automatically), Noise Cancellation, lightweight, leatherette ear cushions, flexible microphone boom, adjustable headband and Tangle-Free coiled Quick Disconnect cord. OvisLink Call Center Headsets are designed for users who work in call centers, service centers or sales departments and talk long hours on the phone. This Headsets service users with solid, superior clear sound quality and all-days comfortable. OvisLink Lifetime Factory Warranty is included! (* AT & T has many different telephone models. This headset is only compatible with Syn248 Business phones model SB35025 and SB35031. If you have AT&T SynJ phones, order OvisLink headset model OVHS084-ATT ASIN # B01LOS58QC instead.)OvisLink 2-Year Warranty Policy: You may send defective headset to OvisLink address (in U.S.A.) for repair anytime. Physical damage, devices damaged from lightning, flood, fire, electrical, water and software update, other "acts of god" are not covered by our warranty policy.