Vehicle horn horn. Bicycles often have a classic "bulb horn", operated by squeezing a rubber bulb attached to a metal horn. Squeezing the bulb forces air through a steel reed located in the throat of the horn, making it vibrate, producing a single note. The flaring horn matches the acoustic impedance of the reed to the open air, radiating the sound waves efficiently, making the sound louder. Other types of horns used on bicycles include battery-operated horns (sometimes even car horns on 12-volt circuits are incorporated) and small air horns powered by a small can of compressed gas. Oliver Lucas of Birmingham,
Allen (brand) Allen (brand) Allen is a brand of hand tools, most widely recognized for its wrenches, known generically as "Allen wrenches". As a brand, it is owned by Apex Tool Group. Originally named Allen Manufacturing Company, the business produced hexagonal set screws and wrenches to fasten them. The terms "Allen wrench" and "Allen key" are derived from the Allen brand name and refer to the generic product category "hex keys". W.G. Allen filed the first related patent in 1909 for its recessed hex-driven safety screws, a safety improvement over fasteners which protruded from machinery. Apex Tool Group currently manufactures Allen-branded products