An electric shaver (also known as the dry razor, electric razor, or simply shaver) is a razor with an electrically powered rotating or oscillating blade. The electric shaver usually does not require the use of shaving cream, soap, or water. The razor may be powered by a small DC motor, which is either powered by batteries or mains electricity. Many modern ones are powered using rechargeable batteries. Alternatively, an electro-mechanical oscillator driven by an AC-energized solenoid may be used. Some very early mechanical shavers had no electric motor and had to be powered by hand, for example by pulling a cord to drive a flywheel. Electric shavers fall into two main categories: foil or rotary-style. Users tend to prefer one or the other. Many modern shavers are cordless; they are charged up with a plug charger or they are placed within a cleaning and charging unit. History The first person to receive a patent for a razor powered by electricity was John Francis O'Rourke, a New York civil engineer, with his US patent 616554 filed in 1898. The first working electric razor was invented in 1915 by German engineer Johann Bruecker. Others followed suit, such as the American manufacturer Col. Jacob Schick who patented their first electric razor in 1930. The Remington Rand Corporation developed the electric razor further, first producing the electric razor in 1937. Another important inventor was Prof. Alexandre Horowitz, from Philips Laboratories in the Netherlands, who invented the concept of the revolving (rotary) electric razor. It has a shaving head consisting of cutters that cut off the hair entering the head of the razor at skin level. Roland Ullmann from Braun in Germany was another inventor who was decisive for development of the modern electric razor. He was the first to fuse rubber and metal elements on shavers and developed more than 100 electrical razors for Braun. In the course of his career Ullmann filed well over 100 patents for innovations in the context of dry shavers. The major manufacturers introduce new improvements to the hair-cutting mechanism of their products every few years. Each manufacturer sells several different generations of cutting mechanism at the same time, and for each generation, several models with different features and accessories to reach various price points. The improvements to the cutting mechanisms tend to 'trickle-down' to lower-priced models over time. Early versions of electric razors were meant to be used