Expandable Module for TOWERMAX-KSU 240v Protection * Protects up to 4 CO Telephone Lines * 2 CO Pairs Per Jack * Protects Pins 3,4,5,6 on a RJ11/RJ45 Jack RJ11/45 Compatible * 3 screw install to any TOWERMAX Module* Can be used by Itself with Proper Ground Connection Auto Resetting Solid State Sneak Current Protection * UL/CSA (Replaces GUM0502)