Fluke's Bleeper mR - Personal Radiation Monitor 

Bleep rates for background radiation: Approx. 1 bleep every 15-30 minutes.

Energy Range: 45 keV to 6 MeV (±25%)
Dose rate response: Linear to 5 R/h (±20%)
Display: LCD 0.1 mR to 999,999.9 mR