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HOW CELLULAR WORKS AMCI divides a metropolitan service area into a network of cells, each equipped with a low-powered radio transmitter/receiver controlled by a sophisticated computer. Each cell is a vital link between the mobile phones in its geographic area and the telecommunications network of the world. Cellular mobile telephones look very much like regular push-button telephones but with modifications that make them easier to use while driving. Within each phone is a microprocessor chip that controls transmissions and receptions to and from the cells. When the user dials a telephone number and pushes the SEND button on the phone, it signals the nearest cell that a "line" (or radio channel) is desired. The cell instantly connects the phone to an available individual channel and then to our Mobile Switching Center (MSC). The MSC connects the call to the public telephone network, enabling local calls, long distance and even international service. The MSC is the heart and brain of the system making continuous communication possible even as the subscriber drives through a service area. Its computer continuously monitors the signal strength of all mobile phone calls in progress. If any signal becomes weak as the vehicle travels away from a particular cell's sphere of influence, the MSC electronically asks nearby cells if any are receiving a stronger signal from that vehicle. If so, the MSC selects an idle radio channel at the new cell and instructs the mobile phone transmitter-receiver to tune to the new frequency and location. At the same time, the MSC transfers the call's connections with the public telephone system to the new cell channel. This entire procedure takes less than 0.2 seconds, a time so short that the "hand-off", as it is called, is undetected by the users. They only know that their conversation continues uninterrupted, and that they are hearing each other "as clear as a bell". Because a cellular system uses low-powered radio transmissions between cell sites and mobile phones, the communication channels available to the system can be used again and again within a metropolitan area. This combination of cellular structure and low-powered transmissions enables the system to provide service to virtually an unlimited number of users. Once the construction of the "cell" is complete and the transmission equipment is fine tuned, visitation to the cell site by service personnel for customary maintenance will occur about once every three weeks in a station wagon or panel/van type vehicle. The cell is entirely self-monitored and connects directly to a central office where sophisticated computers alert personnel to any equipment malfunction or breach of security. The cellular transmission equipment and the operation of the cell site does not endanger public health, safety, comfort, morals or general welfare. Cellular transmissions do not affect other public or private transmissions, including radio, CB, television, ham or public service communications. It should be noted that since the first cellular system became operational in the Chicago metropolitan area on October 13, 1983, and since all subsequent systems have become operational, including the Milwaukee, Madison, Janesville, Cincinnati, Detroit, Dayton and Columbus systems, AMCI has yet to experience a single instance where their transmissions have caused interference with other forms of electronic transmissions or communications. amci.mad\woo 132\cell ular.how