Streetlights use bypass technology. Through use of either isolation transformers or film cutout technology, streetlights are able to pass the voltage through to other streetlights when they are burned out. Much like older Christmas tree lights, streetlights are connected in series design; the current to operate five streetlights on the same street flows from light 1 through 2, 3 and so on. In the past, when one light burned out, the streetlights after it would not power on since the current could not cross the dead bulb. Isolation transformers carry the current across regardless of a working or nonworking bulb. Film cutout technology uses a film of material that connects the contacts needed for current to flow. If a streetlight burns out, the current bypasses the burned-out circuit and runs along the film cutout.