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Blog  | Topic: [Circuits] | 2 MIN READ TIME

What is an EFM circuit?


What is an EFM circuit?

The aim of EFM is to provide a high speed and reliable IP connection for business users, something that's pretty important in today's world of increasing application traffic. EFM can be used to connect a business site to an IP VPN or Ethernet wide area network (WAN), or to the internet.

Ethernet in the First Mile offers speeds of up to 35Mbit/s. A standard ADSL connection uses just one phone line, but an EFM connection usually uses up to 8 copper pairs (that's 'phone lines' to you and me) in parallel.

This boosts the maximum speed available, enables symmetric bandwidth (same speed in both direction - upstream and downstream) and makes the connection more reliable in case you lose a copper pair down the line...it does happen! 

For performance and reliability, fibre is always preferable to copper.  

Fibre Ethernet circuits support higher bandwidth and are more reliable, but this comes with a higher cost and longer lead time. Copper circuits are affected by electrical interference that causes persistent or intermittent errors and performance issues. The signal processing and re-transmission to overcome these errors also increases latency (the delay in sending and receiving data). This in turn reduces the performance of the circuit and slows down the applications and damages user experience.

Traditionally, businesses had the choice between a standard ADSL service and fibre-based Ethernet services. For some business sites, ADSL is not fast or reliable enough for their needs, whereas fibre-based Ethernet services are too expensive for them.

Happily, EFM sits right in-between ADSL and fibre Ethernet, and is relatively cost effective.

Real-time applications

It's important to ensure when you're looking at installing EFM circuits that will carry real-time applications such as SAP, Citrix and IP Telephony, that the circuit is delivered over a minimum of two pairs and with class of service (CoS). This will give better performance and resilience.

A common practice for some telco providers has been to reduce costs by offering lower speed EFM circuits on a single pair, and not providing CoS as an available option.

When ordering circuits for sites that will use real-time applications, always ensure that:

  • Your provider is using a minimum of  two copper pairs
  • Full details are on the order
  • CoS is an option (even if just for the future)

It will make all the difference!


Copper EFM circuits usually have quicker installation times than fibre circuits. So, if you've left it a bit late to order then a copper EFM circuit may just save your bacon as it only takes 30-45 days, rather than 90-180 days for fibre...!

What speeds can I get?

Just like ADSL, factors like your distance from the exchange will affect the speed you achieve. That said, it ranges from 1-10Mbit/s for an EFM 2 Pair service and 10-20Mbit/s for an EFM 4 Pair service. Some telco's offer more pairs, which gives a faster service further away from the exchange. 

Top tips: Key things to consider with EFM

There are several things you should look out for with EFM. A good managed network provider or network management service will cover all these things...so make sure you check that they do!

  • Ensure the number of pairs the service is delivered on is visible in your monitoring portal
  • During the on-boarding process, check the correct number of pairs is illuminated
  • Ensure that if an EFM circuit is being ordered for a real-time application customer, it's delivered over a minimum of 2 copper pairs. Even for low speed circuits!
  • A photograph that clearly shows the live status of the pairs on the customer premises equipment



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 Editor's notes: Published on April 18 2016

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