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Redwood City Pofice <br /> Departmen# System Description <br /> ` (using the industry standard AT command set) or Motorola's <br /> Native Mode may be interfaced directly with a VRM650. In tuin, <br /> the radio provides the field unit access to the Motorola wireless <br /> data fixed network equipment The VRM650 incorporates <br /> Motorola's advanced, over the air, RDLAP 19.2Kbps protocol for <br /> the highest message throughput and reliability in the systems <br /> employing laptop devices. The VRM650 incoiporates Iviotorola's <br /> 800 MHz mobile radio with the modem in one package. <br /> The VRM650 is designed to withstand the harsh conditions of the <br /> mobile environm�nt. Specifications aze compliant with industry <br /> and Motorola's stcingent standards for durability,reliability, EMI, <br /> RFI,vibration, and shock. <br /> Operation Data Channel Access <br /> . For dedicated, data only applications (i.e.,radio is not shared for <br /> both Data and Voice service), the VRM650 is normally on line at <br /> all times, thereby monitoring all outbound(base to mobile) data <br /> transmissions on the selected channel,but responding on�y to those <br /> messages addressed to it. This process is transparent to the user. <br /> When data is to be transmitted inbound(mobile-to-base),the <br /> VRM650 will adhere to the channel contention rules of the <br /> RDLAP Slotted Digital Sense Multiple Access(SDSMA)protocol, <br /> before asserting PTT on the radio. <br /> Roaming Multiple Site Access <br /> The inbound iransmissions from a VRM650 may be monitored by <br /> multiple DBS's. Each DBS sends this received information to the - <br /> RNC where it is evaluated to determine the best path to tallc back <br /> to the particular radio . This information is stored in the RNC and <br /> used to optimally route messages addressed to that particular radio. <br /> Additionally, each VRM650 evaluates the quatity of the signal <br /> received from the base site it is currently registered to. When the <br /> signal quality degrades enough,the VRM650 will seek another site <br /> with better signal quality on which to register with the RNC. <br /> Therefore, while the MDD is roaming around the coverage azea <br /> provided through multiple sites,the RNC will lmow the proper site <br /> to contact that MDD. This process is also transparent to the user. <br /> Qrrrorowau► . 2' 9 <br /> _ _ _ . __ __ _��.. _ _ _.__ __. _ <br />