Digital Matter Support

G120 Iridium Set Up and Operation


This article is intended as a complete guide to the available Iridium System parameters, and also to describe how the Iridium connection operates on the G120. For a 'cheat sheet' - see the G120 Iridium Quick Start Guide

The G120 has the option of being connected to an Iridium Edge module.

The Iridium Edge module contains an Irdium SBD modem and antenna, which allows the G120 to send data when the cellular network is not available (e.g. out of mobile coverage areas). 

Because of the higher costs of Iridium SBD data, the G120 firmware has been designed to allow it to be configured to only send a subset of the normal data based on the applied parameters. 

Upon returning to coverage the full data set (stored in device memory when out of coverage) is uploaded to the server. 

System Parameters

Default System Parameters (Iridium Disabled) are shown below.

Iridium Set Up Check List

1. Install Iridium Edge Modem and device according to the wiring diagram/install guide <link to this>

2. Enable Iridium Parameter set to Yes

Steps 1 and 2 are the minimum requirement to have a device connect via Iridium.

3. If any input changes are required to be transmitted via Iridium (e.g. duress buttons), the input mask must be set. 

This is a bit mask. To determine the bit mask:

a) Represent your required bits in binary, e.g if we require Digital Inputs 2 and 3 to be sent when they become active over Iridium), the binary representation of this is 1100 - bits 3, 2, 1, 0 

Binary bits are counted from right to left, and the right most (least significant) bit is bit 0

b) Convert this representation to decimal via an online calculator or Windows Calculator


c) Enter the decimal representation in the parameters - in this instance 12. 

3. Set out of GSM coverage timeout and in trip logging period if alternate parameters are desired. 

Default Behaviour + Iridium Logging

For a device on defaults, when in coverage it will log and upload according to it's regular parameters e.g.

- Hourly Heartbeats

- Beginning and end of trip positions and uploads

- 30s time, heading change, distance travelled, speed change, etc changes during a trip. 

Switching To Iridium

The G120 will always attempt to send data on the cellular network as a priority. 

If the GSM modem cannot REGISTER on the network within the Out of GSM Coverage Timeout (5 min default), then the assumption is made that the modem is out of GSM coverage the Iridium Modem will be used. 

As soon as the GSM Modem gets signal and is able to register on the network then the Iridium connection will no longer be used. 

Iridium Logging

The following records will be uploaded when the G120 is using Iridium. 

Trip Start and End

This will always be logged and sent when on Iridium

Digital Inputs

Optional logging and uploads of Digital Inputs 0 to 7, if configured in the parameter masks. Allowing for important inputs to be sent e.g. panic buttons. 

Periodic In Trip

A position update is sent every In Trip Logging Period (default 10 mins as per Iridium parameter tab shown above)


Accident log reasons will always be logged and uploaded, giving an immediate notification of this. 


When out of trip, it will heartbeat according to it's Iridium heartbeat parameter - which is specified as a multiple of the GSM heartbeat. 2 hours by default. 

Note the device will still log (but not upload) all the same records that it would while in GSM coverage and store these in memory. This means the complete, 30 second, turn by turn trip record data will be sent to the server upon returning to GSM coverage. 

Records Sent over Iridium

Given we only have a 20 byte record (see Record Size below) to work with, only a subset of the complete data is sent with each Iridium upload. The message will contain, 

  • The log reason (why the record was generated) - e.g. Heartbeat, Trip Start, Elapsed Time
  • Trip Status bit - to say if it is currently in or out of trip
  • Sequence Number + Date Time
  • GPS postion - Lat and Long
  • Current speed
  • Current Heading
  • Digital Inputs 0-7

Record Size

Each Iridium upload uses a 20 byte record

In order to estimate your required usage you will need to estimate how long the G120 will be operating with no GSM coverage and what your parameters are set to. 

See Choosing an Iridium Data Package + Calculator

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