User's Manual

COMPANY CONFIDENTIAL
RF-TWACS Based AMR System DCSI CUSTOMER PRODUCT SPECIFICATION
May 30, 2003 Application Notes – Rev. 1 7
must alternately share. (The same unit cannot simultaneously transmit on one frequency
while receiving on another). This causes all two way communication to be half duplex.
FSK, Frequency Shift Keying. Modulation technique where‘1’/’0’ transmission occurs
by means of frequency shifting. One frequency is used to represent the logical ‘1’ and a
different frequency to represent the logical ‘0’.
Link, A path between two units in a communications system.
Manchester encoding, A signal transmission method defined for the representation of
binary data bits on the radio channel. Manchester encoding specifies two “half-bits”, so
that a guaranteed mid-bit transition occurs in the transmitted signal.
RSSI, Received Signal Strength Indicator. This feature available in the receiver portion
of the circuit measures the strength, relative to a noise background, with which a signal
is obtained.
RX, Receive / Receiver.
Session, A series of transactions exchanged between two units in a communication
system within each other communications zone.
TR, Transceiver
TX, Transmit / Transmitter
Data Related Terms
Frozen Read, The transponder sees many readings in the course of a day. It can be
programmed to save one of them as the official “frozen read” for a given time of day. In
the case of a hard-wired solution, the read can be performed at a set time of day. For an
RF link, the end devices are set to perform a read at the appointed time, then transmit it
some time later during the hour. The receiver in turn captures the transmission time-
stamped nearest the appointed time and applies it as the “frozen read”.
Interval Read, Is the relative amount of consumption registered by the metering device
over an interval of time. The standard interval for this design is 1 hr. Therefore, we speak
of hourly interval data – the amount of consumption that occurs in one hour time.
Present Read, The most up-to-date reading available from the meter. For an integrated
module such as an EMA, the energy consumption can be obtained immediately. For cases
where the TWACS gateway is not integrated within the meter being read, there is a
certain amount of data latency. In the case of the RF link, the system should broadcast an
update hourly. The “present read” then becomes at most one hour old, and on average a
half hour old.
Shifted Read, In metering terminology, when a copy is made of a register, it is called
“shifting.” The idea is that a snapshot of a given register is made by copying the present