Digi M10 - Manual (Page 13)

Digi m10 Technical Overview
Digi International, Inc. © 2009 Page 13 of 26
3.2 Gateway Earth Station (GES)
The role of the Gateway Earth Station (GES) is to provide an RF communications link between
the message switch and the satellite constellation. It consists of medium gain tracking antennas,
RF and modem equipment, and communications hardware and software for sending and
receiving data packets. The GES equipment and site are designed for unattended operation. The
GES uses radome-enclosed, VHF full-motion antennas with approximately 17 dB of gain. Two
fully independent antenna systems, and associated RF and control equipment, provide complete
functional redundancy at a GES site.
3.3 Subscriber Communicator (SC)
The term Subscriber Communicator (SC) refers in general to the satellite modem or a device
incorporating a satellite modem.
3.4 SC Terminated
Messages sent to the SC from the GES
More documentation can be found on the kit installation CD. To learn more, navigate to
C:\Program Files\Digi\Digi m10 JumpStart Kit\documents please refer to either ORBCOMM Serial
Interface Specification > SC-TERMINATED MESSAGE or ORBCOMM Serial Interface
Specification > Figure 4.8 SC-Terminated Message.
3.5 SC Originated
Messages sent from the SC to the GES
More documentation can be found on the kit installation CD. To learn more, navigate to
C:\Program Files\Digi\Digi m10 JumpStart Kit\documents please refer to either ORBCOMM Serial
Interface Specification > SC-ORIGINATED MESSAGE or ORBCOMM Serial Interface
Specification > SC-ORIGINATED MESSAGE.
3.6 Global Gram
Global Gram messaging, or store-and-forward message transfer, is available in instances when a
satellite is in view of a satellite modem, also referred to as Subscriber Communicator (SC), but
there are no ORBCOMM gateways connected to the satellite. Examples of such instances
include ocean areas and locations where there is no gateway, but regulatory approval for a
satellite modem to communicate with a satellite has been granted. Global Grams allow satellites
and satellite modems to archive short messages when the destination ORBCOMM gateway is