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The strengths and benefits of an ED-137 compliant recording solution

Air Traffic Control

Reading time: 10 minute(s)
Oddmund Johansen

Oddmund is the CEO and Founder of GuardREC AS. With more than 20 years of experience in the recording industry, Oddmund has extensive knowledge helping organizations in both ATC and Bank & finance with their recording and compliance requirements.

VoIP recording solutions might just be the best answer to stricter regulations, higher standards and an ever-growing demand for greater efficiency in the ATC industry.

The Air Traffic Control industry adheres to some of the world’s strictest requirements and regulations, and as such there is an ever-growing need for flexibility, reliability and cost efficiency in order to ensure compliance to the constantly expanding set of rules. 




Airport communication is no exception. Industry standards require all communication by air traffic controllers and aircraft to be recorded and stored securely, and to satisfy these requirements efficiently the industry saw the need for an alternative to conventional analogue or digital communication systems.

This led to the introduction of Voice over Internet Protocol (VoIP) communication and recording – an IP connectivity solution offering far more flexibility and opportunities than outdated and expensive analogue and digital systems in the midst of being phased out.

With it came a new set of requirements – The Interoperability Standards for VoIP ATM Components, also known as ED-137.


The shift from passive to active recording

As with all new technologies VoIP recording systems have had to overcome a few challenges as the standards were established and developed, among them issues with performance and timing.

Those issues have now been resolved, and ED-137 compliant recording systems are being adopted by airports across the globe.


There are, however, still a few things you need to be aware of.

ED-137 specifications clearly state that “recordings SHALL be based on active sessions opened from clients”, yet some providers still offer passive recording systems that bypass the standards and requirements by using port mirroring and decoding of the ED-137 protocol.

Because ED-137 requires you to handle data through an active connection using these methods, and systems, effectively means that you are not compliant in accordance with the standards. In addition, these systems are far likely to experience connectivity issues. 


Check out our webinar on Recording and Replay of ED-137


Ensuring compliance to industry regulations and directives

Here at GuardREC our main focus has always been compliance.

The flexible guardREC® recording solution is built to support analogue, digital and VoIP systems, and has implemented the EUROCAE ED-137 specifications to give you full protection.

By choosing our recording system and servers you have the opportunity to take full advantage of the innovative new technologies, and you will always be compliant with the latest regulations and directives in the industry.


Automatic setup allows for quicker configuration 

Using an ED-137 compliant system makes configuration both easier and quicker due to the automatic setup of all channels. The recorder will automatically establish the recording channel as soon as it receives a request from the client, without the need for manual intervention.

Channels may be established according to a variety of criteria, such as frequency, operator position or users, or a combination of these. All you need to do in order to get your channels set up is to define how interactions between the clients and the recorder will be mapped.

Considering the fact that many airports may have as many as 800 separate channels a VoIP recording solution provides far greater efficiency than the older, analogue systems where all channels would have to be patched manually.

Additionality, it minimizes the risk of human errors during setup.


Easier upkeep and a smoother upgrade process 

The benefits of an ED-137 compliant recording system’s automatic set up is not limited to the initial configuration.

The system also makes upkeep easier by automatically registering and connecting to a new channel when equipment or hardware connected to the system (e.g. a radio) needs to be replaced.

An automatic set up also makes the process of implementing upgrades or extensions to the system smoother and quicker, however, this only applies if the system in question is designed in such a way that it allows for easy upgrades in order to keep up with continuously developing standards and requirements.

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Separating RX and TX audio streams

There is currently an exciting suggestion in Revision C of ED-137 to separate RX and TX audio streams, thus allowing analysis of air traffic controllers’ communication, emotion and stress detection and perhaps even speech-to-text options.

Until now, this has been almost impossible to do due to the mixed frequencies, poor sound quality on incoming calls and difficulties distinguishing air traffic controllers from pilots.

By interfacing outgoing calls, you will hear the air traffic controllers’ communication perfectly and may be able to identify early indicators that the controller in question is showing signs of stress or exhaustion. 

The guardREC® recording system supports multi-channel recording and is primed and ready to receive separate audio streams.


Misconceptions about ED-137

One widely discussed topic regarding ED-137 is performance. Many have voiced concerns about the performance abilities of IP connectivity systems.

 In a properly designed VoIP recorder performance should not be an issue. Computers and software used in airports today are more than capable of handling and processing the large amount of calls efficiently.

The issues concerning performance are most likely connected to providers not being able to satisfy ED-137 requirements, rather than the VoIP software itself.

There’s also a misconception that ED-137 compliant recording systems require less storage space than its analogue or digital counterparts. While this might be the case compared to older recording systems, there is no significant difference is storage space requirements when comparing VoIP solutions to modern analogue or digital systems.

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ED-137 standards still need more precise definitions

While there are many benefits to using an ED-137 compliant system, there is still room for improvement. In my opinion the ED-137 standards are still too loosely defined, allowing too many options and “mays”. 

This wiggle room within the requirements enhances the need for verifying the setup upon installation. A plug test or third-party test does not necessarily tell the whole truth, and thus relying solely on these types of tests may have unfortunate consequences – one of them being loss of data.

To minimize the risk of data loss you need a mechanism in place in your recording system that will alert you of possible losses before it’s too late. In many recording systems the loss of data is only discovered upon an attempted retrieval of the recording, and by then it is too late.

Another issue with the current ED-137 standards relates to installation. When connecting to two or more providers for the first time you may face significant challenges. Despite claiming to be compliant, chances are the system might not be a hundred per cent operational. This highlights the need to have an alert mechanism in place within the system to signal if something seems out of the ordinary.

Both of these issues could be resolved by tightening up the ED-137 standards, making them stricter and more precise.


A flexible, reliable and ED-137 compliant recording system 

Here at GuardREC we aim to be even better and more reliable than the current standards require.

Offering a modular and very flexible architecture, our recording system allows for great quality, simple configuration and easy addition of new modules and services. It also simplifies IP connectivity and implements the newest technologies in cyber security.

This flexible connectivity between the recorder and the recorded devices paves the way for new opportunities, such as centralized recording systems located in a single hub servicing multiple airports. 

Our VoIP solutions also allows you to take advantage of technologies not available through non-modular and outdated recording systems, e.g.:

  • Recording as-a-Service
  • Private Cloud / Centralized Storage

 At GuardREC we look forward to, and aim to contribute to, further developments in ATC technology. That is why our dynamic and customer driven recording and replay solution is built on the promise of transparency, quality and innovation, tailored for IP connectivity (while maintaining compatibility with analogue and digital solutions) and invested in cyber security.

Brands that trust us

For ATC and Bank & Finance compliance officers, guardREC™ is a recording and replay solution that is built on the promise of transparency, quality and innovation. Our technology is trusted by some of the biggest brands and companies in ATC and Bank & Finance:


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