DCS/PLC and SCADA control systems, though they provide immense capability, share a common weakness. Both are subject to cyber attack from external sources. The potential impact of this vulnerability should not be dismissed. An annunciator system can be put in place that will monitor critical process elements and provide notification of abnormalities. The systems, whether hardwired or software based, are isolated, allowing them to act as a failsafe or backup to the main control and monitoring system.

1. A P P L I C A T I O N N O T E
Annunciators as a “watcher”
for your most critical processes
INTRODUCTION
SOLUTION
DCS (distributed control system)/PLC (programmable logic controller) is the basic control element of any type
of industrial control system. It may be a centralized system with one or several CPUs interconnected through a
communication network. DCS/PLC systems have distributed digital and analog input networks to get informa-
tion from field sensors and transmitters. Processed information is fed into digital and analog output networks to
operate motors, transducers and actuators. Their CPUs have custom-made preprogrammed ladder software to
process information.
These software-based systems are vulnerable to cyber attacks. Most of the industrial control networks (CAN,
PROFI, Control Area, Ethernet and RS485) connect to the internet or other computer networks which are not
fully protected from hackers and viruses. Present day industrial DCS/PLC control systems come with redun-
dancy systems to eliminate shutdowns in case of DCS/PLC hardware failures. However, this does not protect
your DCS/PLC system from any type of cyber attack. Without proper protection, the safety and/or operation of
your plant or business are put at great risk.
PROBLEM
SCADA (Supervisory Control and Data Acquisition) is custom
made PC base software that can drag required information
directly from a connected DCS/PLC system to be graphically
displayed on a monitor screen. The latest SCADA systems
come with various types of attractive graphics displays, multi
screens and event data records with touch sensitive input
buttons. These systems are viewed as attractive options for
space saving because the entire control panel can be incorpo-
rated into a single monitor screen.
ADVANTAGES
1) Generates quick audible alarms for operator attention -
maintains alarm state until the problem is sorted out.
2) Annunciator system is not affected by any type of cyber
attack due to its standalone and software free features.
3) Comparing sensor alarms of Annunciator and DCS/PLC
systems, sensor errors in either system can be identified.
4) Easy to identify active alarms displayed in a window annun-
ciator in comparison to a flood of alarm messages displayed
on a SCADA screen. It is very important that operators quickly
respond to critical alarms.
A third-party “watcher” (not another field operator) can look after abnormalities in your process. A standalone
annunciator system equipped with a set of digital inputs from field sensors and lampbox outputs in the control
room will work as a failsafe for DCS/PLC/SCADA systems. These isolated hardwired annunciator (or isolated
software) systems can generate unmistakable alarms and audible warnings when there is an abnormality and
can ultimately save your plant from a potential disaster.
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2. ADVANTAGES CONTINUED....
5) Window annunciator systems do not require
weekly system restarts.
6) Software-free individual alarm modules make
Ronan Annunciator hardware the more reliable
choice in comparison to DCS/PLC hardware.
7) You can expand or modify annunciator systems
without affecting your process operation. Additions
or modifications to DCS/PLC/SCADA alarms may
require plant shutdowns/downtime.
X16PDM
Annunciator
System
Field Signal Inputs
Lamp Box
Display -
Control Room
SCADA PC-Base
LCD Screen/HMI in
Control Room
Field Actuators,
Pump, Motors,
etc...
Digital & Analog
Outputs
to Actuators
Control Signal
Inputs (DCS/PLC)
Digital and Analog
Inputs from Field
Sensors
Hardwired
Process Layout
X71 Graphic
Displays
DCS/PLC/SCADA Process Control System + Annunciator System + Wired Graphic Display
Alarm Management accomplished through annunciator systems - critical alarms are never missed by operators
RONAN ANNUNCIATOR SYNOPSIS
System
Software-free annunciators
Ronan Explosion Proof X19
Ronan Explosion Proof X11SN
Software-based w/ Remote Monitor
Ronan Event-Recording X11CB
Ronan SER X500F
Technical Differences
Relay-based single-point annunciator
Software-free CPLD-based annunciator
Software-based remote annunciator
Sequence of events recording system
X11SN
Solid-state
Annunciator
Software-free
Software-free
Isolated from network
Connected to internet
Software-free paths
Software path isolated
X500F Multiplexer
(MUX)
X500F Sequence of
Events Recorder
Control Room
www.ronan.com | sales@ronan.com | (800) 327-6626
Software
for remote monitoring
from main network