A system camera or camera body is a camera with interchangeable components that constitutes the core of a system. Early representatives include Leica I Schraubgewinde (1930), Exakta (1936) and the Nikon F (1959). System cameras are often single-lens reflex (SLR) or twin-lens reflex (TLR) but can also be rangefinder cameras or, more recently, mirrorless interchangeable-lens cameras. Voice coil motors(VCMs) are used to control the lens movement to achieve fast and accurate autofocus. The VCM moves the lens elements to focus the light onto the sensor with high precision. Even point-and-shoot cameras usually include a tripod socket. A system camera includes at the very least a camera body and separate, interchangeable lenses, whence the alternative name interchangeable-lens camera (ILC). In addition it often includes: While some early mechanical interfaces are standardized across brands, optical and electronic interfaces are often proprietary. Hot shoes have a common interface for basic flash functions, but often contain proprietary contacts inside for advanced flashes and data modules.