User's Manual

TWACS
®
- ORION
®
for CENTRON
®
Meter User Guide 3
Installation and Operation
Theory of Operation
The DCSI TWACS
®
- ORION
®
system operates within the 916.450 MHz
UHF radio frequency range on channel 43A. This unlicensed frequency band
is known as the ISM (Industrial, Science, and Medical) band. All components
in the DCSI TWACS
®
- ORION
®
system comply with FCC (Federal
Communications Commission) rules and regulations for radio devices
operating in this frequency range.
This band provides up to 79 channels; the TWACS
®
- ORION
®
system uses
51 of these channels. A channel is defined as a pair of adjacent frequencies
used for transmission and for reception. Refer to the note below.
Because the FCC limits the amount and duration of channel energy that can
be emitted during RF transmission, the TWACS
®
- ORION
®
system employs
transmission Frequency Shift Keying (FSK). This modulation and frequency
hopping technology serves to:
• Comply with FCC regulations
• Reduce potential interference to and from other devices operating in the
same band
• Reduce the potential for eavesdropping
• Minimize the effects of signal reduction
N OTE Frequency hopping employs an algorithm that provides a half duplex (one
transmission direction at a time [send or receive]), pseudo-random
sequence of frequencies for the two-way radio link.
Frequency Shift Keying modulation controls data transmission by
“frequency shifting” between two frequencies (a channel). One
frequency is used to represent the logical “1” and a different frequency
represents the logical “0”.
Five channels provide link acquisition with the HHTR while the remaining 45
channels are used for data transmission after a successful link is established.
The one remaining channel is used for TWACS-ORION communication.
The EMTR retains data until new data is uploaded during an ORION session.
If an ORION transmitter is removed from the Remt List table stored in the
EMTR, the previously loaded data (for the removed ORION transmitter) is
automatically deleted.