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Essential Guide to Telecommunications, The, Third Edition by Annabel Z. Dodd

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Specialized Mobile Radio—Originally Voice, Later Data

Initially, the 800 to 900 MHz range of specialized mobile radio spectrum was used for voice applications. Examples of customers who use these services are contractors and concrete companies. They push a microphone button to talk. Conversations between the mobile units and from mobile units to a central site are private. These systems have no interconnection with the public switched telephone network. This spectrum was later used for analog data-only service by ARDIS, now merged with AMSC (American Mobile Satellite Company) and RAM, now part of Cingular Wireless. Eventually, companies such as Nextel Communications used the spectrum for digital services to sell voice, data, paging and short ...

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