What essential features do I need in a remote terminal unit?
Don't waste time and money sending a technician to a remote site miles away simply to turn a switch. A remote terminal unit with control relay outputs will let you operate remote site equipment directly from your NOC.
Discrete alarm inputs (also called digital inputs or contact closures):
These are typically used to monitor equipment failures, intrusion alarms, beacons, and flood and fire detectors.
Terminal server function:
Your remote terminal unit can also serve as a terminal server to remote-site serial devices. Your devices connect to the remote terminal unit's serial ports, giving you immediate Telnet access via LAN from your NOC at any time.
A remote terminal unit that supports ping alarms will ping devices on your network at regular intervals. If a device fails to respond, the remote terminal unit will send an alarm as an SNMP Trap, providing immediate notification that the device has failed or gone offline.
Analog alarm inputs:
While discrete alarms monitor on/off conditions, analog alarms measure continuously variable levels of voltage or current. Analog alarms monitor temperature, humidity and pressure, all of which can critically affect equipment performance.
Would the size of my site make a difference on the type of remote terminal unit I would need?
Yes, finding the right capacity remote terminal unit for monitoring your site would vary depending on your size. You can use the following as a basic guideline:
Select a small remote alarm unit like the NetGuardian 216 for cell towers, remote huts, or enclosed cabinets (16 discrete alarms, 2 analog alarms, SNMP)
Select a medium remote alarm unit like the NetGuardian 832A for remote switches (32 discrete alarms, expandable to 176 discrete inputs, 32 ping alarms, 8 analog alarms, 8 control relays, 8 serial terminal server ports, SNMP)
For central offices or regional hubs, select a large remote alarm unit like the modular Advanced Telemetry System (scalable from 96 to 1,824 discrete alarms, 48 to 864 analog alarms, 32 to 576 controls, SNMP or TL1)
What is a ping alarm?
A ping alarm is an automatic alert sent to you when one of your LAN connected devices fails to respond to successive pings. Modern alarm monitoring equipment, such as a remote terminal unit, can be configured to send scheduled pings to a large number of devices every few minutes (some remote terminal units support ping alarming to as many as 32 distinct IP addresses simultaneously.
Which remote terminal units (RTUs) have ping alarm support?
The NetGuardian family of remote terminal units, designed and manufactured by DPS Telecom, has broad support for ping alarms. Most devices support ping-based monitoring of 32 different IP addresses. A NetGuardian can alert you via alarm master, pager, email, cell phone, or web interface when a user-defined number of consecutive pings to a device fail.
What does the term "alarm point" mean within the context of remote terminal unit operation?
An "alarm point" is the logical term for a single sensed lead the activation of which represents an event that is generally thought to be an alarm condition. There might be a sense lead connected to a low oil probe in a generator or a monitored entry door.
What does the term "point map" mean within the context of remote terminal unit operation?
A "point map" is a single MIB leaf that presents the current status of a 64 alarm point display in an ASCII readable form where a "." represents an alarm point with an inactive sense lead and an "x" represents a point with an active sense lead.
What characteristics of an alarm point can be configured through software? For instance, can point 4 be used to sense an active-low signal, or point 5 to sense a level or edge?
The NetGuardian alarm points are level sensed and can be software configured to generate an "alarm" condition on either a high or a low level.
Can I provision my remote terminal units and upgrade their firmware remotely?
Yes, with the NetGuardian you can. For all units with upgradeable firmware, you can upgrade via craft port or serial port. You can provision remotely and even queue firmware upgrades for your entire fleet of remote terminal units with one click.
The NetGuardian user manual talks about 8 control relay outputs. How do I control these output ports?
You can control these output ports via web interface or a Telnet session using HyperTerminal, ProComm, or other terminal software. This allows you to remotely activate backup generators, lights, door locks, and other devices.
How can I alert my technicians of alarms at the site as they are exiting?
Wire a light near the exit door to a NetGuardian control relay, then setup a derived control that will activate the light when specified alarms are set.
What is a DCS?
A distributed control system (DCS) is a broad term referring to a process in which the controlling elements are distributed throughout, rather than controlled centrally. In more general terms, a DCS is a process that requires separate computers at each step of the process.