The Klaxon 11 works on the electromagnetic principle. Wire is wound around a steel core causing it to become magnetic as electricity flows through it. This attracts the spring steel diaphragm toward the core. As it approaches the core it forces open a set of points, breaking the flow of electricity causing the core to loose it's magnetism thus allowing the diaphragm to move back out. As it moves out the points close and the cycle is repeated.
In both horns it's the in/out movement of the diaphragm that generates sound waves.
Klaxon 11 was used on 1929 and 1930 KJs and Super/Xs. 8C was used on mid to late twenties De Luxe's and Super/Xs. I'm unsure how far back it's use goes. Horns below do not have the snouts on them (they were car horns and I'm waiting for some shorter motorcycle snouts for them). The snouts fold over on the edge and horns with the snouts attached will measure slightly larger in diameter (click pics to enlarge, use your browser's back button to return):
|Klaxon 11 with snout and diaphragm removed, a hint over 5 inches in diameter. You can see the points above the 2.5 inch mark.||Klaxon 11 back cover is secured by a single screw in the centre. Cover is a larger diameter and not as deep as an 8C back cover. Has a notch out of one edge to clear the terminals.|
|Coil and points can be seen. Opposed blades for wire terminals is a distingushing feature.||Comparision of original (top) and repro (bottom) tags. This original tag does not have "MADE IN" on it and used a nicer font for the 11. I've also seen originals that were the same as the repro.|
|Klaxon 8C with snout and diaphragm removed, 4 1/4 inches in diameter. Toothed gear visible above 2 inch mark.||Klaxon 8C back cover is secured by a single screw offset to one side.|
|Good shot of the motor. Interestingly only a single field coil. Some other makes of motor driven horns have two field coils. Terminals are threaded studs on edge of horn main body.||It's an optical illusion that the repro tag looks longer. If I switched their positions the original would look longer.|
|Here's a shot of a repro Klaxon 11 that belongs to a disappointed friend. These were coming out of Europe in the early 1990's. The size and shape is similar to a Klaxon 8C, but terminals are on back cover.||Faux Klaxon 11 tag specifically made to fit smaller diameter. Also the tag is smooth rather than etched.|