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E-Carrier System: A Brief History of the Protocol and an Overview of the Benefits

A brief history of the E-Carrier system.

The European Conference of Postal and Telecommunications Administrations (CEPT) originally standardized the E-carrier system, in order to provide an industrial standard for digital transmissions of voice and data. The E-Carrier system, which revised and improved the earlier American T-carrier technology, and this has now been adopted by the International Telecommunication Union Telecommunication Standardization Sector (ITU-T) for its reliability and cost-effectiveness.

Functionally similar to the method used in the United States, E-Carrier systems allow for rapid transmission of data over a wireline network.

What is E1 Protocol And How Does It Work?

An E1 link operates over two separate sets of wires, usually Unshielded twisted pair (balanced cable) or using coaxial (unbalanced cable). A nominal electrical signal is encoded with pulses using a method avoiding long periods without polarity changes. The line data rate is split into 32 timeslots, each being allocated 8 bits in turn. Thus each timeslot sends and receives an 8-bit PCM sample, usually encoded according to A-law algorithm, 8000 times per second. This is ideal for telephone calls where the voice is sampled at that data rate and reconstructed at the other end. The timeslots are numbered from 0 to 31.

This standard in communications is now widely used in almost all countries outside the US, Canada, and Japan.

What Are The Practical Uses For E1 And How Can It Benefit My Network and Monitoring System?

If you work in telecom in the United States, you're probably familiar with T1. E1 is very similar, in that it's just a data connection. You can use it to send data of various types.

One potential problem is that E1 is not standard IP LAN. This creates a need for translation equipment that "breaks out" LAN at a remote location that needs it.

How can I effectively manage my network of E1-based facilities?

There are multiple challenges to remotely monitoring and controlling sites with E1 connectivity only.

  • You need a remote monitoring device, and most RTUs support LAN only.
  • You have a variety of equipment at the site that only supports LAN.
  • An OSP site that only has E1 is likely very remote and requires excellent monitoring of batteries, generators, etc.

Any solution to these challenges must have several key capabilities.

  • Communicate using E1.
  • Break out LAN for devices that don't support E1.
  • Remote monitoring and control: discrete inputs, analog inputs, and control relays.
  • Advanced handling of generator monitoring, battery monitoring, etc.
  • High reliability, because the site is likely very remote.

Case Study: National Grid Corporation of The Philippines Deploys E1-Capable Remote Telemetry Units and Master Stations.

NGCP's new overarching monitoring system, built around E1, is composed of E1-capable NetGuardian RTUs, E1 WAN muxes, VLAN routers, and a T/Mon LNX master station. It enables remote monitoring and diagnostics for equipment that was formerly managed with many disconnected systems. Full E1 case study...

NGCP was able to pull off this level of integration by working with a manufacturer who was capable of implementing custom functions (ex. E1 connectivity) into an already-proven RTU design. They also worked with a local rep in the Philippines to make sure they had a smooth deployment. Their rep, Okuda Sangyo Philippines, had previously attended factory training at DPS Telecom headquarters. This gave them the confidence to leverage the DPS philosophy of perfect-fit customization to develop the exact E1-based monitoring system that they needed.

Developing a custom product offered another advantage for NGCP: they knew that their future plans could be accommodated. When you buy off-the-shelf equipment and integrate it yourself, you are effectively becoming your own systems integrator. Only you will be able to support it, because no vendor is aware of what you're doing. One of your parts can be discontinued tomorrow, and you'll have to rework your design.

Working with a manufacturer who custom-tailors a device for you means that you'll get a manual. You'll get tech support. You'll get guaranteed compatibility with future deployments. The Philippines is a complex place for a power utility to operate. There are over 7000 islands in the country. With such demanding circumstances, the team of NGCP engineers are sure to encounter unexpected and unusual requirements as they continue their rollout during the next several years. Having worked with a manufacturer who will make changes, they have a partner to help them easily navigate future scenarios.

Overview of the E1 Remote Telemetry Unit that National Grid Corporation Of The Philippines deployed.

NGCP purchased and rolled out a special build of the NetGuardian 832A that included new E1 functionality. With this modification in place, NGCP was able to utilize all of the 832A's standard features at their E1 locations. These features include:

  • 32 discrete alarm inputs.
  • 8 analog inputs.
  • 8 control relay outputs.
  • RoHS 5
  • Proven design with thousands of deployments worldwide
  • See all 832A features...