User's Manual
Table Of Contents
TWACS
®
-ORION
®
for UMT Products User Guide 11
Chapter 2 • Functional Description
Figure 2.1
RF operation block diagram
During the installation and configuration process, the HHTR-3 and EMTR-3 use
one or more of 51 channels spaced 322 kHz apart in the 902-928 MHz band to
intercommunicate with each other. Control commands and data are input to the
HHTR-3 via the keypad by the installation operator and passed to the EMTR-3
over the RF link. The EMTR-3 acknowledges transmissions from the HHTR-3 and
can read back internally stored data for confirmation of receipt. EMTR-3
transmission occurs only when data is sent or requested by the HHTR-3.
Frequency channel selection is controlled by the HHTR software and is not
operator selectable. Both the HHTR-3 and EMTR-3 operate as intentional radiators
under Section 15.249 of FCC regulations, with transmitted field strengths limited
to less than 94 dBuV/meter. These units use frequency shift-keyed digital data at
9600 bps to communicate, and no subcarriers are used. The occupied bandwidth of
the EMTR-3 or HHTR-3 transmissions is 200 kHz. Both the HHTR-3 and the
EMTR-3 devices have permanently atttached integral antennas and use single
integrated circuit RF transceivers.
HHTR Data
RF = PIC
18
LF
242
902 -
928
MHz
UI = PIC
18
LF
6720
8
MHz
7.
2
V NiMH
1600
mAH
Regulated to
5
V an
d
3.3V
EMTR-3 Dat
a
Orion Dat
a
916 .45
MHz
Data Rate =
100
kbps
2-
level FSK +/
-
50
Khz
(3
o
f
6)
Orion Transmitter
Orion Transmitter
HHTR
Handheld
Transceiver
PC
Data Transfer
from
/
to
HHTR
FOCUS with
EMT
R
-3
RF Interface
Orion Transmitter
Orion Transmitter
RF Operation Block Diagram
(
TWACS
-
Orion Project
)
June
22, 2007
Wire Interface to
Water/Gas Meter
Encoder
1-
way RF Link
902- 928
MHz
Bi
-
Directional
RF Lin
k
RS
-
232
Multi-port EMA provides 1 Electrical port
and 7 RF
p
orts for
g
as/water.
EMA unregulated voltage is 6V to 13V.
EMA regulated voltage is 5V.
Re
g
ulated fro
m
EMA to EMTR-3 is 3.3V.
PIC18F 4525
8MHz
F
CC
ID
:
P
N3
Y
7
2
553
-1
Orion Transmitter
Orion Transmitter
Orion Transmitter
DRAFT