As we often mention lighting is complex. Shunted and non-shunted sockets, or tombstones, is one of those topics that seems to scare off a lot of our customers. Knowing which sockets to use for your lamps is very important. Using the wrong type can not only void the warranty on your light but also cause an electrical short, resulting in a fire hazard, melting the sockets and/ or tubes. Using the wrong type almost always shortens the life of the lamp, as well.
When you hear the word "shunted," think "joined" or "connected." Shunted sockets feature internally connected electrical contacts. This provides a single track for the electrical current to travel from the ballast, through the tombstone, or socket, and to the lamp's pins.
Non-shunted sockets have separate contacts –– or points of entry for the wires –– creating two tracks for the electrical current to travel. Non-shunted sockets have contacts that are not joined/ connected.
Because there are exceptions to this visual difference, however, the safest, most certain way to figure out what kind of sockets you have is to use a voltage meter. Most voltage meters will either light up, ring or beep if the electrical contacts are connected, or shunted.