Viking Electronics HF-3W Two-Way Handsfree Talkback Amplifier System, Improved audio circuitry, Alert tone, Selectable "Push-to-Talk" feature for noisyenvironments, 28V DC talk battery, 3 watts of paging power, The HF-3W handsfree paging unit allows employees to respond to a paging message without reaching for the telephone, It is perfect for use in city desks, shipping and service applications where quick answers are needed, The HF-3W generates its own talk battery and will interface with unused trunk ports on PABX's and key systems, and single line phones, as well as some telephone systems with a two-way paging port and a contact closure.