Path: utzoo!attcan!utgpu!jarvis.csri.toronto.edu!mailrus!ames!henry.jpl.nasa.gov!elroy.jpl.nasa.gov!gryphon!vector!telecom-gateway From: covert@covert.enet.dec.com (John R. Covert 28-Aug-1989 2106) Newsgroups: comp.dcom.telecom Subject: Re: Cellular Telephone Causes Airline Fire Alarm Message-ID: Date: 29 Aug 89 01:16:52 GMT Sender: news@vector.Dallas.TX.US Lines: 26 Approved: telecom-request@vector.dallas.tx.us X-Submissions-To: telecom@eecs.nwu.edu X-Administrivia-To: telecom-request@vector.dallas.tx.us X-TELECOM-Digest: volume 9, issue 330, message 4 of 9 >Does anyone know the differences that make use of private cellular phones >"dangerous" and the use of public cellular phones on planes "safe"? FAA regulations prohibit the use of all electronic devices not explicitly certified to be safe. Radio receivers and transmitters emit electromagnetic waves at frequencies that may interfere with an aircraft's communications or navigation equipment. The "Airphone" public phones aboard aircraft are specifically designed and tested to ensure that they will not interfere with the aircraft. FCC regulations prohibit the use of cellular phones aboard aircraft for a totally different reason: There are only 832 channels allocated for cellular service. In order to allow more than 832 calls to be active in a system, the channels will be reused only a few miles apart. The more customers a system has, the more cell sites it will have (and cell sites will be found in low, rather than high, places), the smaller the coverage area will be for each cell, and the lower the power your cellular phone will be told to use (by the cell site). This allows frequency reuse. If you are at 10,000 feet, your signal is going to reach not only the nearest cell site, but also several other cell sites using the same frequency. You will interfere with other calls. "Airphone" uses a separate group of frequencies. /john