This part is a kind of semiconductor called AT2079-41.
Function of this product has AT2079-41.
Manufacturers : ETC
Image and pinout :
Some of the text within the PDF file :
AT2079/41 154-064M HV 25 KV FV 3.5-6.7KV SV 0-650V 154-064P HV 25.8KV FV 4-8.1KV SV 100-1130V HV 22.5KV FV 3-6.2KV SV 0-620V 154-064V 154-177B HV 27.1KV FV 3.9-6.9KV SV 0-830V HV 22.6KV FV 3-6.3KV SV 0-630V 154-177E HV 22.3KV FV 3-6.2KV SV 0-580V [ ... ]