Monitor 4 & 4EC Handheld Radiation Alert® Detector The M4 and M4EC are compact, general purpose survey meters capable of detecting alpha, beta, gamma, and x-rays over 3 selectable ranges. A red count light flashes and a beep sounds with each event detected. The Monitor 4EC offers a more linear reading for gamma and x-rays ( above 40 keV). Monitor 4 is a halogen-quenched uncompensated GM tube with thin mica window 1.5-2.0 mg/cm2 thick. Monitor 4EC is a halogen-quenched GM tube, energy compensated sidewall 2mm thin filter. Thin mica window 1.5-2.0 mg/cm2 thick. Effective diameter of window is 9.1mm (.36 in.)