The L7591 Subscriber Line Interface Circuit (SLIC) Protector is designed to protect line-feed circuitry from fault-induced lightning and power-cross surge pulses. If a fault current forces TIP and/or RING to a more negative voltage than VS, current is conducted through the trip circuit. When the specified trip current level is reached, transistors PNPN1 and/or PNPN2 will turn on and "crowbar" the majority of the current to ground. If similar pulses force TIP and/or RING to a more positive state than ground, diodes D1 and/or D2 will conduct the pulse to ground. The L7591 SLIC Protector is available in an 8-pin, plastic DIP (L7591AB) and in an 8-pin, plastic SONB package (L7591AS).