towerMAX RS-2 from ITWLinx is an RS-232 line protector with Auto-Resetting Technology, which protects 8-wire RS-232 lines. The PTC resistors open when a surge occurs, protecting your equipment, but unlike other fusses, the PTCs close again once the surge passes. The unit offers expandable system protection using towerMAX Series Base Units. They also feature Signal Perfect Circuitry for auto-resetting surge protection for data networks, telephone and coax lines with RJ45 termination type.