A two-terminal avalanche junction surge suppressor for surge-protective application on systems with dc to 420-Hz frequency and voltages equal to or less than 1000 V rms or 1200 V dc is considered. The device is a single package that may be assembled from any combination of series and/or parallel diode chips. Definitions, service conditions, and a series of test criteria for determining its electrical characteristics are provided. These devices are used as surge diverters for limiting transient overvoltages in power and communications circuits.