This part of IEC 61643 is applicable to avalanche breakdown diodes (ABDs) which represent one type of surge protective device component (hereinafter referred to as SPDC) used in the design and construction of surge protective devices connected to low-voltage power distribution systems, transmission, and signalling networks. Test specifications in this standard are for single ABDs consisting of two terminals. However, multiple ABDs may be assembled within a single package defined as a diode array. Each diode within the array can be tested to this specification.