This standard applies to 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. The avalanche junction surge suppressor is a semiconductor diode which can operate in either the forward or reverse direction of its V-I characteristic. The device is a single package which may be assembled from any combination of series and/or parallel diode chips. This standard contains definitions@ service conditions@ and a series of test criteria for determining the electrical characteristics of these semiconductor avalanche junction surge suppressors. If the characteristics differ with the direction of conduction@ then each direction of conduction shall be separately specified.1 Arresters are covered in ANSI/IEEE C62.1-1984 [1] 2@3 and ANSI/IEEE C62.33-1982 [2]. The tests in this standard are intended as design tests as defined in ANSI/IEEE Std 100-1988 [4] and provide a means of comparison among various avalanche junction surge-protective devices. Semiconductor avalanche junction surge suppressors are a class of diodes that are designed to conduct the surge currents necessary to provide transient overvoltage protection in electrical circuits. Other types of diodes may exhibit surge capability. Unless their surge characteristics have been defined according to this specification@ they should not be used as surge suppressors. Avalanche junction surge suppressors exhibit a relatively high impedance at normal system voltages before and after the surge. They limit surge voltages on equipment by providing a low impedance to conduct the surge discharge current. More specifically@ this standard applies to such devices having a monotonic increase in voltage with increasing current flow. Test criteria and definitions in this standard provide a common engineering language beneficial to user and manufacturer of surge-protective devices. 1Diodes used in the forward direction only for the purpose of surge protection may also be tested in accordance with these specifications. 2The numbers in brackets correspond to the standards listed in the Bibliography@ Section 7 of this standard. 3ANSI/IEEE publications can be obtained from the Sales Department@ American National Standards Institute@ 1430 Broadway@ New York@ NY 10018@ or from the Institute of Electrical and Electronics Engineers@ Service Center@ Piscataway@ NJ 08854.