Patent ID: 8521454

Claim:
A circuit interrupter apparatus comprising: a circuit interrupter comprising: separable contacts, an operating mechanism structured to open and close said separable contacts, and a trip mechanism cooperating with said operating mechanism to trip open said separable contacts, said trip mechanism including a zone selective interlocking input and a zone selective interlocking output; and a device comprising: a first input electrically interconnected with said zone selective interlocking input, a second input electrically interconnected with said zone selective interlocking output, and an indicator circuit structured to indicate that both of said zone selective interlocking input occurred at said first input and that said zone selective interlocking output occurred at said second input, wherein both of said first input and said zone selective interlocking input are electrically connected to a zone selective interlocking input conductor external to said circuit interrupter, wherein both of said second input and said zone selective interlocking output are electrically connected to a zone selective interlocking output conductor external to said circuit interrupter, and wherein said indicator circuit is further structured to analyze timing of said zone selective interlocking input at said first input and said zone selective interlocking output at said second input.