Up until 1946, when Christmas lighting production resumed after World War II, by far the most popular style of electric Christmas lights in use were the series wired type, which meant that if one bulb failed, the entire string went out. Many a frustrated decorator was often relegated to dreaded "search and replace" duty, spending the better part of a December evening searching for that elusive burnt out lamp. Covered on this page are some industry attempts at solving this most frustrating problem...
Apco brand series light tester, designed to make finding a burnt out lamp a bit easier. The user was to grip the wires coming from the light socket firmly with the device, which would puncture the covering of the wires and short out the socket. If the string lit, the the defective lamp was found, if not, then the user would proceed to the next socket and so on. This device added greatly to the fraying problem frequently found with series wired lighting sets.
1923 patent application for Detect-O-Lite system
Many Thanks to Bill Nelson! www.oldchristmaslights.com
[This message has been edited by Webmaster (edited 08-08-2003).]