System Planning Corporation GTLITEV3 Manuale Utente

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GT Lite Operation and Maintenance Manual 

 

GT  Lite  defaults  to  US  frequencies.    Switching to other frequencies is handled by the main 
application using the time since last transmission and GPS data.  Rough GSM based geo-

zones reside in GT Lite memory.  After a failed GSM transmission, the application uses these 
geo-zones to determine which frequencies to search.  If no GPS information is available or if 

there are 5 consecutive failed transmissions, the application will switch back and forth 
between US and EU frequencies every other transmission attempt until a successful transmit.  

If  the  device  is  determined  to  be  in  a  cellular  dead  zone  (e.g.  on  a  vessel  at  sea),  the 
application code delays frequency searching until entering a geo-zone with cell 

communications. 

The frequencies are also selectable locally at the device.  If US or European frequencies are 
selected at the device, GT Lite will default to the selected frequency. 

GT Lite has the option to add Orbcomm satellite communication for near real time 
communications anywhere in the world.  The ORBCOMM system is a Low Earth Orbit (LEO) 

constellation that allows two-way communication to and from mobile or fixed Subscriber 
Communicators (SCs).  In most applications, a message or other data is first generated by an 

SC.  From that source, the data is transmitted to the nearest ORBCOMM satellite.  The 
satellite downlinks the data to the selected Gateway Earth Station (GES), which then 

transmits the data to the desired Gateway Control Center (GCC).  Within the GCC, the data is 
processed and forwarded to its ultimate destination by the Gateway Message Switching 
System (GMSS).  The destination may be another SC, a pager, a corporate resource 

management system or any personal or business e-mail or Internet address.  If the satellite is 
not in view of any GES, it will store the message until a GES is seen and forward it at that 

time.  For more information about the Orbcomm option, please consult Section XXXXXXX. 

GT Lite has the option to add Iridium satellite communication for real time two way 

communications anywhere in the world.  The Iridium system is a LEO constellation that allows 
real-time, two-way communication between the GT Lite and the IMB.  The data is passed 

from satellite to satellite before reaching an earth station, so there is no need for a store and 
forward system.  For more information about the Iridium option, please consult Section 
XXXXXX. 

ZigBee Wireless 

The ZigBee wireless link is a low-cost, very low-power, two-way wireless communications 

standard.  The IEEE 802.15.4 standard defines the lower two layers: the physical layer and 
the medium access control (MAC) sub-layer.  The ZigBee Alliance builds on this foundation by 

providing the network layer and the framework for the application layer. 

The IEEE 802.15.4 standard has two physical layers that operate in two separate frequency 

ranges: 868/915 MHz and 2.4 GHz. The lower physical layer covers both the 868 MHz 
European band and the 915 MHz band that is used in countries such as the United States and 
Australia.  The higher frequency layer, 2.4 GHz, is used virtually world-wide, and is the band 

to be used for GT Lite functions. 

ZigBee  allows  GT  Lite  includes wireless communications with enabled devices and other GT 

Lites.  The mesh network configuration allows  buried  GT  Lite  devices  may  be  able  to 

  Prepared:  R. Straz 

Date: July 25, 2007 

 

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