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11
Chapter 2
Technical Description
2
T
ECHNICAL
D
ESCRIPTION
2.1 System Description
The RMAS-120 consists of a transmitter and a receiver unit used to monitor
conditions at an RF Repeater site.
The standard RMAS-120 communicates data by means of telemetry signal
amplitude modulated on the microwave carrier signal passing through the RF
Repeater. This data stream is recovered at the receiver terminal site by
connecting the alarm receiver unit to the radio AGC output contacts. In order for
proper operation, microwave radios must meet sensitivity and tracking
specifications
—
see Section 1.5.5
,
Terminal Microwave Radio Requirements
,
page 7.
The RMAS-120 data transmission rate is 34 bps, 68 baud with an amplitude
modulation of approximately 1 dB P-P. This slow data speed and low-level
modulation ensure that the RMAS-120 does not interfere with normal radio link
performance of virtually any type of analog or digital microwave radio such as
155 Mb/s OC-3 rate; in 64 QAM or 128QAM radio systems.
The alternative RMAS-120 system includes the standard transmitter module and
UHF telemetry radio link or SNMP Ethernet equipment. Selected alarm point
closures and telemetry measurements generated in the standard transmitter are
transported by the UHF telemetry radio to the receiver location. The UHF radios
operate in 900 MHz ISM band. This band is license free in USA, Canada and
many other countries but not all. See the UHF Installation Guides for more detail.
There are 21 possible alarm and monitoring points
—
see Table 2.A
.
Table 2.A
Alarm Monitoring Points
Analog Points
Battery A Voltage
Battery B Voltage
Battery Bank Temperature
Uncommitted Alarm
Digital Points
Battery A Major
Battery B Major
Amplifier Fault (up to 8)
RF Power Fault (up to 8)
Cabinet Door
Waveguide Pressure
Uncommitted Alarms (up to 7)