The Line EMI Meter measures electromagnetic interference in a single-phase AC power line. It plugs into a wall outlet (mains socket) and requires no battery. It immediately displays total line noise in millivolts (range 1999 mV, resolution 1 mV) in the frequency range 10 KHz 10 MHz (the frequency limits at which sensitivity is ½ of the maximum sensitivity). A speaker plays the sound of the EMI, amplitude demodulated, in order to identify the EMI source (such as an AM or shortwave radio station vs. a motor vs. an electric arc).