The TISP61089S is a dual forward-conducting buffered p-gate overvoltage protector. It is designed to protect monolithic SLICs (Subscriber Line Interface Circuits) against overvoltages on the telephone line caused by lightning, a.c. power contact and induction. The TISP61089S limits voltages that exceed the SLIC supply rail voltage. The TISP61089S parameters are specified to allow equipment compliance with Bellcore GR-1089CORE, Issue 1. The SLIC line driver section is typically powered from 0 V (ground) and a negative voltage in the region of -10 V to -75 V. The protector gate is connected to this negative supply. This references the protection (clipping) voltage to the negative supply voltage. As the protection voltage will then track the negative supply voltage the overvoltage stress on the SLIC is minimised. Positive overvoltages are clipped to ground by diode forward conduction. Negative overvoltages are initially clipped close to the SLIC negative supply rail value. If sufficient current is available from the overvoltage, then