Plantronics MX10 Universal Amplifier for Headsets Intended for: headset, phone Battery: 2 x AA Type Manufacturer warranty: 2 years warranty Adapts almost all telephones for use with a variety of Plantronics headset styles Easy to install and use Separate controls allow independent adjustment of outgoing and incoming volume Switch between headset and handset with a single button Near-universal compatibility with single- and multi- line telephones