What device did Harold P. Kopp secure a patent for in 1941 as the first dedicated electronic voltage surge suppressor?

Zap Trap

Harold P. Kopp is specifically credited with creating the first dedicated electronic voltage surge suppressor, which he named the Zap Trap, securing the patent for this device in 1941. This invention functioned as a small box where one plugged the wall adapter into the box and then the television or other electronic device into the box itself. Although the concept was revolutionary for consumer electronics protection at the time, it predates the development of the highly effective Metal-Oxide Varistor (MOV) by nearly three decades. Therefore, the suppression technology likely relied on older methods common for lightning arresters, such as gas discharge tubes or spark gaps, even though the core concept of limiting surge voltage before equipment reached it was established.