User's Manual

COMPANY CONFIDENTIAL
RF-TWACS Based AMR System DCSI CUSTOMER PRODUCT SPECIFICATION
May 30, 2003 Application Notes – Rev. 1 8
value of a dynamically moving register into a static register. Both the “present read” and
“frozen read” represent shifted readings.
Total Consumption (TC), Is the total amount of consumption registered by the device
since installation. Rollover of the count (to zero) may occur at some point during the life
of the product. Units of measure vary by service and model.
STU, Serial Time Unit. Is the unit of measure for DCSI’s proprietary Serial Time system.
Serial Time measures the number of 2.5 second intervals after midnight. Midnight
(00:00:00) corresponds to “0 STUs”. Five seconds after midnight (00:00:05) corresponds
to 2 STUs. Likewise the Serial Date is the number of days after Jan 1, 1900. This differs
from the commonly used units for time. The ANSI C12.19 standard supports a variety of
methods, the nearest ones of which measure the universal (GMT) time since midnight Jan
1, 1970 in minutes, or the local time since midnight in seconds.
4 SYSTEM OVERVIEW
4.1 General System Theory Overview
The RF link between TWACS transceivers uses a range of frequencies between 902 MHz
and 928 MHz. This range is divided into 79 channels. Fifty channels are needed to satisfy
the FCC’s minimum channel set requirements, so 50 of the 79 were chosen for use.
Five of these 50 channels are reserved for link acquisition and the other 45 are used for
link maintenance (packets transmitted after a link has been acquired). The acquisition
channels are spaced evenly throughout the upper end of the 50-channel set. The 45 link
maintenance channels are used in a random manner while a link is active between
transceivers.
The radio transceivers are equipped with folded dipole antennas. Folded dipoles were
chosen because of their broader radiation pattern as compared with regular dipoles, this
guarantees a better radio coverage under a variety of field installation conditions utilities
may find.
Operationally, TWACS transceivers can play one of two roles during an RF session: A
transceiver that requests a link is the requestor transceiver. A transceiver that replies to
that request is an acceptor transceiver.
TWACS transceivers can be characterized by their roles as shown in Table 1:
Transceiver Type Can request a link from… Can grant a link to…
EMTR Acceptor None an RMTR or an HHTR
RMTR Requestor an EMTR or an HHTR None
HHTR Both an EMTR an RMTR
Table 1 – Roles of DCSI’s Radio Transceivers