User's Manual

12 TWACS
®
-ORION
®
for UMT Products User Guide
System Overview
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 attached integral antennas
and use single integrated circuit RF transceivers.
Electric Meter Transceiver (EMTR-3)
The EMTR-3 is an electronic module assembly (EMA) that is installed in a
TWACS-enabled meter. The EMTR-3 is connected to the UMT transponder
during meter/transponder integration. The EMTR-3 adds functionality to the host
UMT. It does not communicate over the power line but provides data on-command
to the UMT when queried.
The EMTR-3 can communicate with up to seven ORION
®
transmitters. Data from
the ORION
®
transmitter is relayed to the EMTR-3 at each communication session.
This data is relayed upon request to the UMT via I
2
C communication and is
accessed by the TNS across the TWACS network.
The EMTR-3 listens (for 2.5 seconds) for communication from an ORION
®
transmitter. Then, for 2.5 seconds the EMTR-3 listens for an HHTR-3. This pattern
cycles continuously.
Figure 2.3 Electric Meter Transceiver (EMTR-3)