`- Provides headset interface for phone without a headset jack
- Adjustable amplification of headset transmit and receive
- Powered by 12V power supply (included) or 2 AA batteries (optional)
- Headset On/Off button
- Mute button
- Headset volume control
- In-use indicator LED
- 3 RJ11 ports for headset, telephone handset, and telephone