This software is to enable people to use the GM-45 or the GM-10 radiation detector manufactured by Black Cat Systems under GNU/Linux. Two versions of the GM-10 and GM-45 are available; one includes a USB adapter and plugs in to a USB port on your computer and the other version plugs into a standard RS-232 serial port on your computer, and comes with a cable for the standard 9 pin PC serial port. Currently gm4lin is a C program which is able to read data (using the serial interface) from virtually any number of these detectors (sensitivity can be selected individually, per detector e.g. because you want to use a GM10 instead of the GM45, or because you want an activity measurement with Cs137 instead of Co60) and output it to the screen, to a file or to a MySQL database. You can do the acquisition of several detectors simultaneously. It can record the number or particules going through the detector's chamber per minutes or simulate the analog needle of a Bicron RSO-50E detector, a compact, rugged, lightweight ion chamber dosemeter for beta, gamma and X-ray detection and measurements of superficial or deep doses in pulsed or static fields (each particule produces a little signal, with an exponential decay). If the activity you are measuring is quite low, then it could be more interesting to look at each particule at a time. This is the goal of the pulse mode: it shows you every 1 seconds (default value) the charge density decay of the chamber (Pulse mode versus Activity count mode). For more information click here.