Hach-Lange SC 1000 Controller Enhanced Communications - Manual (Page 25)

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Installation
4. Enter the browser password (refer to Section 3.4.1 on page 13 ).
The computer and sc1000 controller are now connected via a secure VPN tunnel.
3.6 Establish a GPRS connection
GPRS is a packet-oriented data service based on the established GSM mobile
communications standard. GPRS enables users to transfer data on the move. In this form
of data transfer, individual batches of data are converted into small data packets, in which
they are subsequently sent. These packets are then reconstructed upon receipt.
If GPRS is activated on the sc1000 controller, there is a seemingly permanent connection
with the receiver ('always-on' operation). However, a radio channel is not opened until
data is actually transferred. Use of a GPRS service is billed not by the duration of the
connection, but by the volume of data sent.
The mobile station (i.e. the sc1000 controller) is assigned a temporary, dynamic IP
address that uniquely identifies it. From the user's point of view, the device is accessed
via this IP address, as is customary on the Internet.
GPRS enables the sc1000 controller to establish an Internet-based connection through
which communication with other Internet users is possible.
The IP address assigned when using GPRS is not usually accessible directly from the
Internet. As a result, requests sent by a GPRS device (e.g. the sc1000 controller) can
only be routed as far as the Internet. Only at that point does the network operator
authorize the response to be routed from the Internet to the GPRS device.
Figure 18 GPRS connections
1 GPRS connection with secure VPN tunnel
2 GPRS connection via a VPN server of the mobile network operator
3 GPRS connection via fixed IP VPN server (only possible if a CDA (Corporate Data Access) account is set up with the
mobile network operator)
4 GPRS connection via a fixed IP service and VPN server of the mobile network operator