The Monitor 4 is a versatile and reliable analog radiation detector that can detect alpha, beta, gamma, and x-rays over three selectable ranges. It is commonly used for various applications such as checking industrial gauges containing Cesium-137, locating radiation sources, personal protection, and general radiation surveying. The device is designed to be simple and ergonomic with a red count light that flashes and a beep that sounds with each count detected. It also features a battery check and a silent operation mode with the flick of a thumb.