The HGLN-DSL Phone/DSL 3-stage Lightning Protector provides superior lightning and surge protection for Telephone and DSL lines. The unit is fully compatible with dedicated and shared DSL and phone lines. Shared phone lines carry the ring voltage for standard telephones. The unit protects against both differential and common mode transients.The first stage is comprised of a differential gas discharge tube. Stage two is a pair of current limiting series resistors and the final stage is a low capacitance diode array. The use of three terminal differential gas discharge tubes provides superior protection against surges. The second stage series resistance limits the power dissipation of the faster diode clamp array in the third stage. This allows time for the slower but higher power gas tubes to turn on. The diode array clamps the leading edge of fast transients to safe levels until the high power gas tubes turn on. This eliminates the damaging leading edge spike that single stage gas tube protectors let leak through. The 3-stage design can handle higher-level transients than a protector that uses only diodes.Hyperlink's HGLN-DSL Lightning Protector has two RJ11 jacks for ease of installation. If terminal strips are needed, use the HGLN-D2 series of surge protectors. A pair of ground lugs and terminals is provided directly on the lightning protector housing, providing superior grounding.For outdoor applications, this protector is also available in a weather resistant enclosure. See AL-DSLJW .