<P> Modern versions of the Geiger counter use the halogen tube invented in 1947 by Sidney H. Liebson . It superseded the earlier Geiger tube because of its much longer life and lower operating voltage, typically 400 - 900 volts . </P> <Ul> <Li> <P> Use of a "hot spot" detector on a long pole to survey waste casks . </P> </Li> <Li> <P> G-M pancake detector feeding a microcontroller data - logger sending data to a PC via bluetooth . A radioactive rock was placed on top the G-M causing the graph to rise . </P> </Li> <Li> <P> G-M counters being used as gamma survey monitors, seeking radioactive satellite debris </P> </Li> </Ul> <Li> <P> Use of a "hot spot" detector on a long pole to survey waste casks . </P> </Li> <P> Use of a "hot spot" detector on a long pole to survey waste casks . </P>

What did the geiger counter read as the count for the background radiation