- DuraFon USL System (UHF, Single-Line) long-range cordless phone system is ideal for an add-on to the DuraFon UHF multi-line system when another port or line is needed- Work as a stand-alone single-line system in environments that only require one line, but still need long-range coverage- Expandable up to eight (8) base units- Works with DuraFon PRO or DuraFon UHF handsets (up to 90)- 12 Floors ( Office / Hotel ) / 3,000 Acres ( Farm / Ranch ) / 250,000 Sq. Ft. ( Warehouse / Retail )- Digital Intercom or