C7 and C9 Christmas Tree Lights
aka Strawberry Lights
C7 and C9 Christmas tree lights resemble the lights we used to have back in the day. And they are still making them,and sometimes with the new technology.
I've got several strings of these Christmas tree lights that I inherited from my grandparents. Every year, I pull them out of the attic and plug them in and they always work. They were manufactured with three wires: white, green and red and if one goes out, they all go out. Every year, my dad would sit me down with several strings of lights that didn't work and a night light receptacle. My job was to take out each bulb and twist it into the night light. Then, I was to plug the light into a socket. If it lit up -- the light bulb was good. It was a very important job. Come to think of it -- could it have been a ploy to keep me out from under foot? Hmmmm.
In the name, the "C" stands for candle. The number in the name, refers to the size of the bulb. In this particular case, a smaller number means a smaller bulb size. A Christmas tree bulb has three dimensions: the total height of the bulb unit (including the receptacle), the height of the bulb itself, and the width of the bulb at the widest point.
The dimensions for a C7 bulb is 2 1/8" total height, bulb height is 1 1/2" with a width of 7/8". A C9 bulb measures out at 2 7/8" total height, bulb height is 2" and the width is 1 1/8".
Personally I love the larger bulbs that are opaque red, green, blue and white. But you can also get bulbs in a clear and transparent colors as well as amber, blue, gold, orange, pink, purple, and yellow. When I think of strawberry lights or C7/C9 lights, I think of the incandescent type light, with the fragile filamented bulbs. Many of the lighting manufacturers and retail stores have been calling these lights "retro" Christmas tree lights. But these lights are now being made in LED, so if you're in the market for new lights this year, keep your eyes open for them.
Most of these lights are on 25' of wire and the spacing is approximately 12" between bulbs. My lights have a clip on the light socket so it can be secured to the branches of the Christmas tree and I've found many newer strings of light have also adapted that design element.