The MASTEC MS2109A is a handheld digital clamp meter that can be used to measure a variety of electrical parameters, including AC/DC voltage, resistance, continuity, AC/DC current, frequency, duty cycle, diode, transistors, and non-contact voltage. It features a large backlit LCD display, data hold function, auto power off function, and a variety of other features that make it a valuable tool for electricians, technicians, hobbyists, and homeowners.