The HiGain HDU-404-L2 is a low-power micro doubler (repeater) unit that extends the range of a HiGain repeaterless T1 transmission system. The doubler units are installed between any doubler-compatible HiGain Line Unit (HLU) and a HiGain Doubler Unit (HDU) or HiGain Remote Unit (HRU). Each doubler allows 1.544 Mbps transmission over an additional Carrier Service Area (CSA) range. The HDU-404-L2 is compatible with both the HiGain and PG-Flex product lines. The CSA includes loops up to 12,000 feet (3.657 km) of 24 AWG or 9,000 feet (2.743 km) of 26 AWG wire.