User's Manual

MRX920 Overview
2-14 MRX920/MTX950 User’s Manual
passed from the antenna to the RF receiver. The RF front end
module then translates the RF spectrum from the 910 - 920 MHz
band down to a 41 MHz band.
Digital Multi-channel Receiver (DMR)
The DMR module receives and decodes the bands from the RF
front end module to determine if the signals are from an RF
module that uses the R900 protocol or other supported protocols.
Samples from up to 8 identified frequencies are processed to
obtain the data signals. The signals are compared to a profile, and
if there is a match, the signal is processed to extract and validate
the data within it. The extracted data is stored in local cache
memory.
The DMR processes 10 MHz of band with a full 128-channel
receiver, of which only 77 channels are available, and extracts
messages which are sent to the CPU. The DMR receives and
demodulates up to eight simultaneous R900 messages. The
MRX920 unit together with the MIU functions as a receiver that
works together as a spread spectrum system.
The MRX920 unit reads signals from R900 MIUs with a high rate of
success on the first pass. Inbound meter readings are collected
and stored into memory. The receiver processes the MIU signals,
and the application software ignores readings from MIU messages
received that are not currently loaded into the unit. Readings from
any MIU that are on one of the routes loaded into the MRX920 unit
will be processed and stored into memory.
The receiver filters out duplicates in order to keep the best or last
reading received. This optimizes memory storage space. Records
for each reading are stored in the receiver database to eliminate
duplicates and to keep track of reading data.
Central Processing Unit (CPU)
The Central Processing Unit (CPU), which temporarily stores
received data, is based on a PC104 board. It receives the messages
obtained from the band by the DMR module through the PC104
(ISA) bus. It then extracts the data and uses an RS-232 serial link
to transfer it to the laptop computer.