A hand-held oscilloscope is a portable or hand-held device used to measure or display a graph of electric signals. It uses a small display or cathode ray tube (CRT) to display electrical or mechanical signals. Oscilloscopes are commonly used in electronics maintenance and design to analyze circuits, debug embedded software and troubleshoot communications networks. They are also used by sound engineers to analyze audio signals. Hand-held oscilloscopes are small and light enough to be carried in a pocket, have minimal features to keep their size and cost down, and have limited input capability. Most have an analog display and usually include automatic measurements. More expensive models may include a digital storage feature, the ability to capture and analyze digital signals, and a digital output.