Box (aka Bank) CCTV cameras are designed to be modular and to accept accessories to fit specific surveillance environments. Box security cameras accept interchangeable lenses with advanced functions. The swappable lenses may feature auto zoom and focus, features that most other cameras do not have (other than the PTZ type). Some box surveillance cameras even allow controlling picture processing functions to enhance video picture output. Generally, box CCTV cameras are not waterproof but there are special alloy bezels that convert box cameras for watertight outdoor use. The box security cameras also do not come with LED IR nigh vision illumination built-in, a standalone donut illuminator is usually inserted over the lens to add IR function.