Looking for a PBX system that uses cell phones as extensions.

Do GSM cell phones transmit anything while looking for a cell tower to connect to?

• What's the truth about cell phones searching for a tower to connect? Is it a passive or active process? About ten years ago I recall reading that: GSM cell phones actively search for cell towers. They send out quite some data in the process. If there are no towers around, they send out stronger signals. This is why the battery runs out faster in no reception area. This is why someone caring for their health and believing that cell phone radio signal can cause bad effects should especially remember to turn off cell phones when in poor or no reception areas. Or, at least, put them into airplane mode. Looking back though the above doesn't make much sense. :-)

• Answer:

  GSM operates in the 900 MHz band (890 MHz - 960 MHz) in Europe and Asia and in the 1900 MHz (sometimes referred to as 1.9 GHz) band in the United States. So all the communication takes place between towers and phones takes place within this band. All the towers create logs, known as "TOWER DUMPS", all the users connected to that tower at any instant are saved in logs and the company or the network provider have access to these files.