Easy to install amplifier connects to most single and multi-line telephones and works with Plantronics quick-disconnect headsets or amplifies the telephone handset up to 26dB. Receive and transmit volume controls. Comes with 10 foot curly cord with quick-disconnect end. Uses 2 AA batteries (included). Amplifier with protection against sudden loud noises, call volume equalizer, and echo management features for increased clarity. Separate control amplifies outgoing voice up to 46dB. For compatibility with 2.5mm jack headsets, call HARC for options.