Lutron EMF-839 is a 3-axis radio frequency electromagnetic field meter 3 Axis probe Wide measuring frequency ranges, 100 kHz to 3 GHz For precision measurement consideration, the meter is included two probes - EP-04L (Low-frequency Probe, 100 kHz to 100 MHz) and EP-03H (High-frequency probe, 100 MHz to 3 GHz) Peak hold function to latch peak value Data hold function to lock the current reading RS232 computer interface Powered by 006P DC 9V battery or DC 9V adapter