User manual
Toolbox 32 User Manual 1.47d www.cse-semaphore.com/mykingfisher
Page
10
2. Introduction
An RTU is electronic equipment that contains a computer. RTUs
are often located in remote places. This led to the name Remote
Telemetry Unit (RTU). RTUs can be wired to a whole range of
devices like switches, relays and sensors. Each RTU can monitor
and control the things it is wired to.
There are two types of devices that an RTU can be wired to -
digital and analog. A digital signal is an ON or OFF state of a
switch or a relay. An analog signal is a variable measurement like
tank level or temperature.
An RTU can also obtain data by communicating with intelligent
devices (eg. a PLC).
RTUs can be programmed to carry out a wide range of tasks. For example:
• Set outputs according to the state of inputs (eg. run a pump to fill a tank that is low)
• Send a message when there is new data or a significant event has occurred
• Perform complex mathematical calculations
Kingfisher RTUs have continued to increase in speed and power over the years and can now provide:
• Data Logging
• Alarming - auto dialing, SMS messages
• Diverse communications - data radios, dialup and cellular modems, leased line, Ethernet and more…
• PLC-like logic processing
• Massive networks - more than 65,000 RTUs
• Support for various protocols eg. Modbus, DNP3
Indirect
Route
RTU3
RTU4
RTU2
Remote
RTUs
Direct
Route
Data
Data
Data
RTU1
Data
Network
RTU2
Data
RTU3
Data
RTU4
Data
Master RTU
An RTU network is 2 or more RTUs that can
communicate with each other in some way. The
communication path is called a route.
Usually one RTU is setup as the Master RTU. The
master RTU regularly polls data from all the other
RTUs. The other RTUs are referred to as Remote
RTUs and can report data changes as they occur
(called exception reports). RTU configuration is
completely flexible and allows for many other types
of communication setups.
This example shows RTU1 as the master and RTUs
2-4 as remote RTUs. RTU3 also stores and then
forwards messages between RTU1 and RTU4.
If only polling is used, it will take up to the regular polling interval before the master RTU knows about new
data from remote RTUs. Eg. If the master polls the remote RTUs every 2 minutes, it will take up to 2 minutes
before the master receives new data from the remote RTUs. If only exception reporting is used, the master
RTU will not know if a remote RTU has failed. If the master RTU does not receive a message from a remote
RTU for a long time this could mean that either there is no new data or that the remote RTU has stopped
communicating.
The best method is to use both polling and exception reports. This means that if a remote RTU fails, the
master RTU will find out about the fail when it performs the next poll. And as soon as data changes or a
significant event occurs, the master RTU will be notified by an exception report.
Kingfisher PLUS+ RTUs (not CP-30 / G30) have three places for storing data: Hardware Registers
(hardware inputs and outputs), Local Registers and Network Registers. When data is sent from one RTU to
another, the data is always stored as network registers in the destination RTU. Network registers are simply
a copy of the hardware and local registers that are received from the sending RTU.
Kingfisher PLUS+ RTUs (except LP-1/2/3 and G30) are comprised of up to 64 modules that plug onto 1 or
more backplanes.