 that provides access to the private packet base station. A private packet network is the backbone, and it may interface into public data networks or be used on a private basis, for a company's own enterprise network. Among the packet data options is Mobitex, a paging network developed by Ericsson (www.ericsson.com). It is an open standard for dedicated wireless data and emphasizes reliability and its use in safety-type applications. It is therefore mainly used by military, police, firefighters, and ambulance services. Around 150 such orga- 1G: Analog Transmission Antenna Packet Laptop Modem Public Network) Private Packet Private Packet Base Station Network Figure 14.3 Packet radio data network architecture nizations use Mobitex, which offers a highly reliable communications channel for data where communication must never fail. Mobitex is a trunked radio system based on X.25, originally operating at 8Kbps and now ranging up to 19.2Kbps, and it is built using a fault-tolerant architecture. It is a packet-switched, narrowband, data-only technology mainly for short-burst data. It is ideally suited for applications such as interactive messaging, e-mail, machine-to-machine, telematics/positioning, and forms-based applications. Mobitex channels are 12.5KHz wide. All Mobitex networks operate in one of five frequency families: 80MHz, 160MHz, 400MHz (gen- erally between 415MHz and 430 MHz), 800MHz (generally between 820MHz and 870MHz), or 900MHz (generally between 895MHz and 910 MHz). Frequencies and channels are generally assigned by national government authorities. Mobitex is offered on more than 30 networks on five continents, but by 2005 it was used primarily in the United States and Canada. European Mobitex networks withered in the face of the overwhelming success of GSM. However, now in its fifth major revision, Mobitex continues to be improved and enhanced for demanding professional use, and the Mobitex Association (www.mobitex.org) reported that its 2005 conference was a great success. The Mobitex system equipment