Welcome aboard, ChaiKneez!
Good question ... the answer has to do with the wireless networks used by the devices.
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You might recognize this protocol as one of the primary protocols being used by cell phones (along with CDMA). You might want to use the 'S' version of the product if you are located in an urban area with good cell phone coverage.
If you're pretty geeky (like me) you would recognize this as the same protocol being used by the HAM radio community to communicate over the Internet. (Fascinating stuff, packet radio.) You might want to use the 'GPRS' version of the product if you are located in a rural area with limited cell phone coverage.
The Nurit 8000 series is the first handheld, wireless terminal that is able to use the GSM/GPRS protocols, and looks to be the market leader in this area, despite some problems with the first units to be released. (The Verifone Omni 3600 product supports the GSM protocol and the CDMA protocol, however it is not able to use the GPRS protocol.)
Most wireless terminals relied/rely on either the outdated CDPD (Celluar Digital Packet Data) protocol, on the Motient/Mobitex network (that was also used by Palm.net before they discontinued the service), or on the current market leader, CDMA (Code Division Multiple Access, a cellular technology orginally known as IS-95). The Mobitex network will be around for awhile, however its coverage is quite limited, particularly in rural areas (see this map for coverage details
). CDMA is still going strong and is in use by many cell phone companies as their primary wireless protocol.
To sum up: The Nurit 8000 series products use the latest and greatest protocols available to handheld, wireless POS terminals (for credit card processing and such). Depending on how the device is set up, it can use either of two popular wireless services. Its ability to tap into the GPRS protocol is very new, and care should be taken to test the devices out thoroghly before your company commits to it.