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Multiple Address System
(MAS) radios from Alligator Communications are designed from
the ground up to deliver SCADA savvy radio communications that
are virtually maintenance and worry free.
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Alligator
Communications was the first to offer:
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Frequency Agile radios with "Over The
Air" adjustment,
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Automatic Global Frequency Calibration (AGFC),
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Automatic Deviation Control (ADC),
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Automatic Level Control (ALC),
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A UCA™ Compliant MAS radio
system, and
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GatorTrac™ for maintaining the
optimum
Bit Error Rate (BER) in MAS radio networks.
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Industries & Applications:
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Utility Data Communications
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Railroad Data Communications
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Oil and Gas Pipeline Monitoring
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Water and Wastewater Systems
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SCADA & Distribution Automation
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A typical Multiple Address Radio
System (MARS) will consist of a master station and four or more remote
stations:
Model
1800A Master Station
The master station connects to a local data acquisition computer or
systems controller either directly, via telephone line, or via microwave
link. More complex systems may include multiple master stations,
repeaters, or polling remotes. The Model 1800A radio is configurable to
fulfill each one of these roles. Details >
Model
1888A Remote Station
Each remote radio connects to a Remote Terminal Unit (RTU), Programmable
Logic Controller (PLC) or Intelligent Electronic Device (IED) that
collects data or enacts received control signals. Details
>
GatorTrac™
Alligator Communications takes MAS operating and maintenance technology to
the limit with GatorTrac™. This patented design features a common time
base in the master/repeater radio to synchronize and align all its
internal modules as well as the associated remote radios.
Even the most sophisticated time base will age. Physics dictates that the
consequence of crystal aging will be a deviation from the "cut"
frequency. This is one of the causes of high Bit Error Rate. However, with
Alligator's GatorTrac™, the premise is that with a common time base,
there will be only one point that can drift. All operating radios in the
network are continuously calibrated against that common time base, and
therefore, the transmitter "signal" will always be precisely
aligned with the receiver "window." As a result, the system Bit
Error Rate (BER) is always maintained at an optimum level.
When the frequency eventually drifts close to FCC allowed limits, the
common time base at the Alligator Master Station can be recalibrated to
the assigned frequency with a single adjustment while monitoring its
transmit frequency. This adjustment, in turn, will automatically
recalibrate all modules of the master station and each of the Alligator
remote radios equipped with AGFC.
With the Alligator master radio, frequency adjustment can be performed
with the Alligator diagnostic software by connecting the PC to its rear
panel or via any RF link. There is no need to use tuning tools or to open
the chassis.
To maintain the true redundancy of the Alligator Master Station, a second
common time base with automatic switchover is provided for activation in
the event of a malfunction of the primary common time base.
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Utility Communications Architecture™ Compliance
UCA™ is an open architecture protocol established
under the guidance of EPRI and NRECA in order to provide "Plug &
Play" capabilities among different devices and software vendors. As
one of the team members in the DA/DSM Demonstration project managed by
United Power Association, Alligator is the first to provide a UCA™
Compliant MAS radio. The Alligator radio is capable of operating in the
conventional polling mode and UCA's enhanced polling with the
"Contention Avoidance" mode of reporting.
Unlike conventional polling, where there is constant
communication between the master and its associated remotes even though
there is no significant data being updated, the Contention Avoidance mode
of operation establishes communication only when significant changes
require the remote sites to report back. Both the master and the remote
radios idle at a non-transmit mode. This approach will greatly reduce the
currently congested RF spectrum and will significantly reduce the risks of
interference.
Self-Arbitrating Radio
This capability, developed for the DA/DSM Demonstration project,
allows remote Intelligent Electronics Devices (IED's) to send relevant
real-time information without the use of traditional polling. This new
ability, coupled with the UCA™ open protocols, will allow SCADA and
Distribution Automation (DA) systems to operate in an unsolicited data
delivery mode that will maximize data throughput and minimize radio
bandwidth utilization. Each remote radio acts as a traffic director, and
only upon the detection of absence of network communication will the
remote radio signal the associated IED to start sending data. In order for
this to work, there must be no RF collision among a network of radios. A
hardware handshake between the IED and Alligator's remote radio can change
the mode of operation. Logic "High" at the DTR pin signals the
radio to be in "Contention Avoidance " mode; whereas, a logic
"Low" will revert the radio to conventional polled mode.
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