GSM

GSM stands for "Global System for Mobile Communications".  Also, GSM is currently the most popular digital cellular type of network in the world, being used almost always in Europe, often in Asia and now at least partially in the Americas.  It should also be stated the Nextel iDen network in the Americas is also very similar in structure to GSM.

GSM is a version of TDMA - a time division multiplex cellular system.  For GSM, what this means is that 8 channels - which means 8 different cellular communication paths - timeshare a single cellular frequency for transmission.  How do they time share?  Picture  8 people standing in a circle.  Every 10 seconds, pretend that a beach ball is passed around the circle, always in the same direction, and always to the person adjacent.  TDMA works very similarly.  For that cellular channel, the data for each conversation or data is given one eighth of the time slot.  How does the voice sound continuous and not broken up at the other end?  The voice is transmitted digitally.  When the voice is recovered from the TDMA GSM data at the receiving end, it is converted into analog audio, and to the listener, appears very smooth and continuous.