Yep, Neil, I'm not even sure how many vehicles use which system anymore, but for many years, most of our cars and pickups had a single dual filament bulb behind each of the red lenses on the back end; one for the tail light and the other for brake/turn signal. As someone else has already said, if you were on the brake and signalling a turn at the same time, the one for the direction of the turn would flash and the other would be on solid. Nowadays most vehicles have the newer system with a separate bulb and amber lense for the turn signal (they also have a third brake light somewhere near the center of the rear end and higher than the tail lights), but most trailers still use the single dual filament bulb. And trailers without brakes usually have a flat 4 wire connector; ground, tail light, right turn signal/brake light, and left turn signal/brake light. If the trailers start using the separate bulbs, there's sure going to be a lot of re-wiring necessary in this country./w3tcompact/icons/laugh.gif