This Russian made detector is an outstanding value comparing favorably with other detectors selling for many times more.  It has two scales...microsievert and microrotengen and a circuit test switch.  To make the reading of the scales "idiot proof"  they are also color coded from green (safe) yellow (caution) to red (danger). Micro means millionth ergo this instument is highly sensitive, especially when compared with the older Civil Defense models of the 60's.  One Sievert (international measurement standard) is equal to 100 REM, One Sievert of doseage is the level at which some people may suffer from radiation sickness with 4-5 sieverts being considered fatal for many.  The instructions that come with this detector are adequate and with the help of a label maker, I was able to "translate" into english all the on-off switches. This detector is so sensitive that I can measure the normal background radiation level of three tenths of one millionth of a sievert!  The DRGB-90 is a nice, small, state of the art precision instrument thats fun to "play" with requiring only 60 seconds for the built-in geiger tube to obtain a reading.  It even chirps!