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Types of RTUs: Which is Best for You?

By Morgana Siggins

December 16, 2019


Selecting the right RTU for your remote sites can be challenging. When you're trying to find the right capacity, interface, and features - all in one device - it might be hard to know which direction to take and what should be prioritized.

Perfect-fit RTUs
A Remote Telemetry Unit (RTU) is used to provide vital information regarding the status of the equipment and other environmental conditions that are important for the site to maintain the service it was designed to provide. The size and scope of the unit will depend on the site and the equipment being monitored.

As a competent remote monitoring systems provider, we know that before choosing an RTU you should consider both its short-term and long-term effects on your network monitoring strategy. It's important that you select an RTU that will both immediately improve your network visibility and support your overall upgrade plan to support your future monitoring goals.

Since not all RTUs will perfectly fit in your current network (ours included), it's important that you evaluate your options and make an informed decision. So, let's get started.

1. Small-sized RTUs

Small remote alarm units have around 16 discrete alarms and 2 analog alarms. These units are perfect for cell towers, remote huts, enclosed cabinets, or any other type of location that doesn't require an expensive, heavy-duty RTU.

Some companies don't monitor small sites like remote huts, collocation racks, or enclosed cabinets. Some don't even monitor large sites if they have fewer than 32 alarm points.

This can be a major mistake. Problems can happen anywhere. Every blind spot in your network visibility, no matter how small, is a place where you won't know about problems until equipment finally fails.

With the density of modern equipment, site size is often a poor indicator of outage impact. Even small-scale network outages can diminish your revenue.

Recurring equipment failures at small sites can eat away at your repair and equipment budgets.

Proactive companies are now actively looking to monitor small sites to avoid these problems.

So, why do network managers run the risks of not monitoring their smaller sites? Because they might think they can't monitor small sites cost-effectively.

Keep in mind that, though, that network monitoring doesn't always mean high-capacity RTUs, dedicated lines, and hundreds of man-hours spent on configuration and databasing.

Smaller RTUs make this kind of thinking possible. They're exactly the right capacity to monitor small sites. You get the alarm capability you need without spending a fortune on alarm capacity you will never use.

2. Medium-sized RTUs

Medium remote alarm units have around 32 discrete alarms, 8 analog alarms, and control relays. They're bet fitted for remote switches, or for any other sites where a large-capacity RTU isn't necessary, but you still need advanced functions (such as a built-in terminal server).

Like a lot of networks, you probably have those "in-between capacity" sites that aren't exactly small, but they don't require a big RTU with capacity you'll never be able to use. Medium-sized RTUs are the "just right" devices for these kinds of scenarios.

3. Large-sized RTUs

Large remote alarm units have around 96 to 1,824 discrete alarms, 48 to 864 analog alarms, and 32 to 576. These RTUs are a good fit for central offices, regional hubs, or any other type of network that presently requires or will require high-density alarm coverage.

How to Determine The Right Size RTU for Your Needs

Most RTUs are equipped with input channels (also called alarm points) for sensing, output channels for control, audio/visual indications for alarms, and communications ports.

If you don't have enough capacity to cover everything you want to monitor, you won't have good network visibility. That's why it's so important to properly calculate how many alarm points you'll need.

To select the correct alarm monitoring capacity for your requirements, review each type of remote site in the network and determine your total number of:

  • Discrete alarms - also called contact closures or digital inputs

  • Analog values or sensors, such as temperature, humidity, current draw, etc.

  • Devices you will need to operate remotely with control relays

At first glance, a survey of your remote site might show that you need to monitor a few basic environmental alarms or a few pieces of equipment. So you may think that you're looking for a system that can monitor around 6 alarm points.

But, is that enough?

Let's take a look at elements of remote sites that require monitoring. Identifying these elements will help you plan your remote site monitoring needs. Also, it will help you choose the right RTU for your specific scenario.

1. Discrete Alarms

As we've discussed before, contact closures are known as alarm inputs, discrete alarms, or digital inputs. Discrete alarm points are those which can be measures in terms of "on/off", "opened/closed", or "yes/no".

When looking for a perfect-fit RTU, your first step will be to determine how many discrete alarm points you need at your site. These are simple binary on/off inputs that you can use for monitoring just about anything.

Here are the items that are commonly monitored as discrete alarms:

  • Intrusions alarms

    Intrusion alarms monitor whether doors, windows, and other access points are open or closed. More advanced monitoring systems will also allow you to control door access to your remote sites. For example, some systems allow you to determine who, when, and which door can be entered.

  • Structure beacons

    If your remote site has lights that warn aircraft of its presence, then you'll definitely want to make sure you have these monitored with an automated system. The Federal Communications Commission (FCC) and the Federal Aviation Administration (FAA) have plenty of rules and regulations regarding tower light monitoring that you should be aware of.

  • Equipment failures

    Many network elements have some type of contact closure that will indicate what state the device is in (critical, major, minor). Obviously, this varies greatly from vendor to vendor. With the right remote monitoring system, you can assign text descriptions to these alarms that coincide with the equipment vendor's definitions. Monitoring your multi-vendor equipment using a single interface is sure to make everyone's job a little easier while increasing your network visibility.

  • Environmental alarms

    These can often be the most critical alarms in the facility. The top two discrete environmental alarms that are monitored are flooding and fire detection. Many remote site operators enhance their visibility by adding a site camera to their monitoring system. There's nothing quite like visual confirmation before resources are directed to a problem that ends up being a faulty sensor.

2. Analog Alarms

Analog alarms inputs usually measure a range of values, unlike on/off discrete alarms. A common example of an analog application is the measurement of temperature.

If you have analog alarm values to measure, you need to define the thresholds at which your monitoring system will take action.

For instance, suppose you are measuring the temperature of a remote site. Building temperatures range from 10 to 120 degrees Fahrenheit. Under normal conditions, the building's heating and cooling system will keep the temperature within an acceptable range. To take advantage of multiple analog values, you might set up 4 different threshold values, such as:

  • When the temperature is below 30 degrees, notify a technician and notify the Network Operations Center (NOC). A value this low might indicate that the heater is not working at all.

  • When the temperature is below 50 degrees, notify the NOC. This may indicate that the heater is not functioning properly.

  • When the temperature is above 80 degrees, notify the NOC. This might indicate that the air conditioning unit is not functioning properly.

  • When the temperature is above 100 degrees, notify a technician and the NOC, as well as open a vent (via derived controls). This may indicate that the air conditioning unit is not functioning at all.

Remember, though, that in order to gain this level of detailed visibility, you need to look for a monitoring system that can accept at least four separate analog threshold values.

3. Control Relays

Your RTU collects a lot of data with its discrete, analog, and other specialized inputs, and that helps to build your situational awareness of a remote location that might be hundreds or thousands of miles away. Sometimes, you'll realize that you need to take action.

Imagine that you have a commercial power failure at a site. You're remotely watching your backup battery levels drop, and - at a certain point - it's time to turn on that generator.

If you don't have control relays on your RTU, you won't be able to turn on a generator that accepts a standard 5 VDC activation signal. Imagine how silly it would be drive out to a remote site to just flip a switch.

That's why most modern RTUs do have control relays outputs. With them, you're able to remotely activate just about any piece of equipment.

Don't Forget to Take Future Growth Into Consideration

Once you've defined your current and long-term network monitoring goals, choose an RTU that meets your present needs and will expand to meet your future needs.

This means that when selecting your RTU, it's important to allow some room for future growth - but within reason. Therefore, it's essential that you accurately measure your real-world needs, then add the correct amount to anticipate future growth. This way you'll avoid ending up with less capacity than you need.

On the other hand, it's also important to make sure you are not wasting your budget money on capacity that you could never use. So, for most companies, the right allowance for future growth is an extra 15% on top of their calculated present need.

Which Kind of RTU is the Best for You?

No matter what size site you need to monitor, you can find a remote that will provide complete and cost-effective coverage. Easy expansion options let you add more monitoring capacity as your network grows.

The bottom line is that you can monitor your remote sites more effectively by choosing remotes of the right capacity for the size of your site. For smaller sites, choosing a light-capacity RTU will save you the expense of buying more than you need. For larger sites, you need to be sure that you have enough capacity to cover all of your equipment.

We've helped hundreds of clients to achieve their perfect-fit solution, and we know that sometimes you might need the help of a specialist to take into consideration things you didn't even know you could monitor.

So, to help you with your remote monitoring system deployment, our team of specialists put together the DPS Remote Site Survey. This quick document brings some practical questions that you will help you brainstorm all of the elements you want to monitor at your remote sites.

You can also get the help of our experts by simply getting in touch with us. We can help you survey your remote sites step-by-step, making sure you don't miss any opportunities to make your network monitoring simpler, more effective - and easier on your budget.

Morgana Siggins

Morgana Siggins

Morgana Siggins is a marketing writer, content creator, and documentation specialist at DPS Telecom. She has created over 200 blog articles and videos sharing her years of experience in the remote monitoring industry.