The 420LE/B series is a two stage transient voltage protector providing primary and secondary protection against lightning, inductive switching and electrostatic discharge (ESD) transient threats. The first stage diverts the transient current through the ground terminal return path and the second stage clamps the voltage to a safe level without interruption of service. The 420LE/B series is designed to protect data lines from differential (line to line) and common mode (line to ground) transients. Terminals 1 and 2, 3 and 4 for the 420LE and pins 2 and 3, 4, and 5 for the 420LB are designated as line pairs. Each line pair is referenced to ground. A transient voltage suppressor is connected across each line pair for differential mode protection. Each line pair is referenced to ground.