The ASCO Model 172 Surge Protective Device is designed to protect two pairs of wires specifically for alarm and security systems where operating currents can be as high as 5 Amps. Electrically, the Model 172 is a rugged series hybrid implementing a staged complement of MOVs, copper wound inductors and Silicon Avalanche Diodes. This design reduces series resistance to 0.2 ohms per pair. These products are intended to mate with a PCB1B gold-plated female terminal connector accessory.