In accordance with an embodiment a device is usable to measure radio frequency (RF) signals including microwave signals to provide an alarm when a power level at its input exceeds predetermined levels. A user can attach the device to a coax cable on a microwave or wireless tower to determine if certain power levels are present and what levels are exceeded. If high power is indicated by the device, the user will then avoid attaching that coax cable to other measurement equipment which would be damaged by excessive RF power. The device is further usable, for example, to apply power to one coax cable in a cable bundle then identify which cable of the bundle is getting the power by connecting the device on the output end of each coax in the bundle, one by one.