A3LA-R-MIL-MOD User Guide Version B
Document Number: 451-93156-001A
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to a specific modem with a phone number to dial, user identification, and password. The
modem can then be used to call another computer, a remote LAN, or an Internet service
provider, as shown in Figure 18. The handshaking and protocols are established between the
modems independent of the landline.
Figure 18: PSTN Dial-up Connectivity
The Iridium dial-up data service, as shown in Figure 19, functions in much the same way as the
PSTN dial-up connectivity. From the perspective of a computer, the Iridium modem is just
another external modem. The only difference is that the dialed telephone number must
conform to the international dialing pattern used by Iridium. When a data call is placed, the
Iridium modem actually dials and initiates a connection with the Iridium gateway through the
Iridium satellite constellation. Because the Iridium modem is requesting to establish a data
connection, the switch at the gateway routes the call through another modem. The modem at
the Iridium gateway then dials into and connects to another modem at the other end. Figure 19
illustrates how an Iridium dial-up data service call is routed. The handshaking and protocols
established between the modems are independent of the Iridium network.
For those ISU-to-ISU dial-up calls where data transmission delay is critical, such as the
application of Transmission Control Protocol/ Internet Protocol (TCP/IP) protocol, DAV should
be considered in the design. This option eliminates the Iridium gateway once authentication
and registration is completed, allowing ISU-to-ISU communication without the gateway in the
loop.
4.4
VDC
RS2
32
NA
L R
esearch
Antenna
PSTN
ISP
(Internet)
Corporate
Network
4.4
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RS2
32
NA
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esearch
Antenna
