Scramblers and descramblers are usually based on linear-feedback shift registers. Specific influences include Lambretta scooters, Honda 305 Scramblers, and Schwinn Black Phantom bicycles. Striding Edge is a notorious accident spot among hikers and scramblers. Black ice is a great hazard for climbers and scramblers. Steel hardtops used on these postal Scramblers and Overlanders were known as "World Cab" tops. The Enigma machines were a family of portable cipher machines with rotor scramblers. AJS scramblers were produced from 1968 until 1974 in 250, 370 and 410 guises. Players can climb different radio towers and remove their scramblers. Spitfire Scramblers also used Gold Star Catalina cycle parts in 1957 and 1963. The Catalina Scramblers in Santa Cruz, CA. Such modifications were commonly known as creating scramblers. The CL72 and CL77 Scramblers also used the same engines. These, in turn, replaced less secure voice scramblers. Those that lighted on her head or shoulders were most prized by the scramblers. Using modern public-key systems, these "scramblers" are much more secure than their earlier analog counterparts.