Power Line Telecommunications (PLT)

27 October 2008

This statement supplements the statement we made on PLT




The PLT Report

Ofcom recently disclosed a technical report on Comtrend PLT products. PLT products use a technology to extend broadband and networks in the home using the domestic electricity wiring.

The purpose of this update is threefold. Firstly, it is to give context to this report; secondly it is to provide clarity on the regulations that relate to this area; and thirdly it is to make further related information publically available.

The Context

The electromagnetic compatibility (EMC) regulatory regime

All electronic products placed on the market in the UK – including PLT devices – are required to comply with the Electromagnetic Compatibility Regulations 2006 (Statutory Instrument number 2006/3418) (the "EMC Regulations"). This implements an EU Directive (204/108/EC).

In summary, electronic equipment (which generates an electromagnetic disturbance) must only be placed on the market if it complies with certain relevant requirements. Equally, Member States must not impede the placing on the market of equipment if it does comply.

The key requirement is that equipment must meet "essential requirements". These are –

  1. that the electromagnetic disturbance generated by electronic equipment does not exceed a level above which radio and telecommunications equipment or other equipment cannot operate as intended; and
  2. that the equipment itself has an adequate level of immunity to electromagnetic disturbance.

Who is responsible for meeting the requirements?

The person who places products on the market, usually the manufacturer or the importer, is responsible for meeting the essential requirements. This is in essence a self certification scheme. The responsible person may carry out their own assessment or present technical information to an accredited organisation known as a "Notified Body" (who may issue an "Opinion" regarding compliance). They may choose to reference relevant technical specifications known as "harmonised standards" (published by the EU). The advantage of using a harmonised standard is a legal presumption of conformity with the essential requirements. This is only a presumption however and it remains open to national enforcement authorities to prove that the equipment does not in fact comply, if that is the case.

Reference to harmonised standards is not mandatory and the responsible person may choose not to refer to one when asserting compliance. Failure to meet a harmonised standard does not mean that there is a failure (or a legal presumption of a failure) to meet the essential requirements.

Ofcom's role under EMC legislation

The UK Government department for Business Innovation and Skill (BIS) is responsible for overseeing the EMC Regulations.

Enforcement powers are delegated to Ofcom where there is a radio spectrum protection or management issue. Ofcom can bring criminal prosecutions and can suspend sales if it believes an offence is taking place.

In connection with our functions we engage with BIS, the EU Commission's Directorate General (DG) Enterprise and other Member States through Administration and Cooperation Groups (ADCO).

The report which has been disclosed

The disclosed report was part of the evidence gathered by Ofcom to investigate compliance with the EMC regime of two types of Comtrend Ethernet Powerline Adaptors as supplied by BT.

Ofcom did not publish the report at the time as it was obtained as evidence for a criminal investigation and the premature releasing of evidence may adversely prejudice the conduct of proceedings in court.

The Information Commissioner found that Ofcom's basis for not disclosing this information was valid. However, it ordered the disclosure of the report because the public interest in disclosing it outweighed the public interest in withholding it. Ofcom was therefore required to disclose the report. For full details of the findings of the Information Commissioners findings see: (http://www.ico.gov.uk/~/media/documents/decisionnotices/2011/fs_50301488.ashx).

Harmonised Standards

There is no suitable standard which is directly applicable to PLT products. This is because it is a relatively new technology and has generated divergence of opinion. In 2001 the EU Commission issued a mandate for the production of a suitable PLT standard. This work is still in progress.

Insufficient evidence

The report concluded that the PLT equipment in question did not satisfy the essential requirements.

Notwithstanding this report, as explained in the September 2009 Statement, Ofcom found at the time of the investigation that there was not a breach of the EMC essential requirements. Ofcom's considerations in that regard were:

  • The EMC regulatory regime is founded in criminal law. For a prosecution to succeed Ofcom must prove beyond reasonable doubt that a manufacturer had placed a particular product on the market and that the product did not meet the essential requirements, because it produced excessive levels of "electromagnetic disturbance".
  • Comtrend had obtained a Notified Body Opinion.
  • Significantly, the conclusions of the disclosed report were based on an assessment against a harmonised standard for (EN55022) which is not specifically intended for PLT apparatus and contained a caveat that it does not consider the communications services that could be affected or the range at which the affect might occur.
  • The testing and analysis is complex and highly technical. For that reason there is uncertainty as to when products fail to meet essential requirements.
  • There is no suitable EU harmonised standard directly applicable to this type of apparatus. So testing and analysis took place against a backdrop of wider technical uncertainty than is normally the case when standards provide an appropriate benchmark.

Ofcom Prosecutions

In considering prosecutions, Ofcom applies the Crown Prosecution Service Code. The two key tests are:

  1. is there on the evidence a realistic prospect of conviction?; and if so
  2. is prosecution in the public interest?

Given that the evidence case for non compliance was not clear (and was complex) Ofcom did not consider that there was a realistic prospect of conviction. Included within that assessment is the fact that given the EMC uncertainty over the benchmark for this apparatus, the prosecutor would essentially be asking the court to determine what the acceptable level of disturbance is. A court would have test results one way and the other, and no extraneous point of reference to measure them by.

Given that the first test on the evidence was not met, there was no need to turn to the second test which relates to public interest. But, Ofcom considered that if that test were to be applied, prosecution would probably not be in the public interest for the following reasons:

  • the companies involved were doing what they could to comply with the EMC technical requirements for this apparatus;
  • There wasn't evidence of serious public harm from the use of the apparatus. There were a relatively low number of complaints (all from amateur radio users) when compared to the number of devices being used. This is not a case, for example, involving harmful interference to aircraft navigation where there would be a potentially significant public safety issue or harm;
  • BT was using other means to solve the problem. BT were sending out their engineers (for free) to fix problems as they arise. It would not seem to be in the public interest to prosecute in relation to an individual case where there is no actual public harm because the problem has been fixed.
  • BT and Comtrend were cooperating with Ofcom's investigations and appeared willing to do what they could to resolve any problems.
  • Rather than focus on companies' individual products it would make sense to address the lack of harmonised standard as a priority. Ofcom could work with the Government to push for a EU resolution.
  • The most appropriate means to resolve any wider problem is the development by the EU of an EMC "harmonised standard" for these products. That will give manufacturers a much clearer benchmark of what is acceptable in relation to these products. Meeting a standard only gives a presumption of compliance in any individual case, but it nevertheless does give a benchmark for measuring performance.

Ofcom also considered (as an aside) the existence of the Commission Recommendation of 6 April 2005 (2205/292/EC) which deals with this technology, although not for the purposes of the above assessment. It does recommend "proportionate" enforcement measures in relation to EMC enforcement for this apparatus. The availability of alternative ways of resolving immediate problems arising from particular cases by BT and the possibility of future EU harmonisation of standards indicate that prosecution in this context might well be disproportionate.

No right to "clean" spectrum

Under the Wireless Telegraphy Act 2006 the rationale for licensing is to separate different users of the radio spectrum in terms of geography, time and frequency.

While the need to avoid harmful interference underpins the regime, individual wireless telegraphy licence holders are not offered a legal or practical guarantee that interference will not arise. Interference can arise from a number of sources outside the control of the licensing authority. For example, atmospheric conditions, pirate radio use and foreign overseas use all have the potential to cause interference. For this reason no guarantees of "reception" of radio signals have been given. The licensing regime instead sets reasonable parameters on the transmission of radio signals.

Licensees do not therefore have a formal legal right to "clean spectrum". Radio frequencies are commonly occupied by a "background noise" and this noise is created from a multitude of sources. Transmission on a radio frequency several bands away could cause a detectable background noise.

Ofcom does understand that amateur radio users are concerned about the potential increase in the background noise floor attributed by PLT equipment, particularly since they may be particularly inclined to use sensitive equipment to listen to weak signals. However, legally amateur radio licence holders are on the same footing as others and Ofcom's ability to deliver "clean" spectrum is limited for the same practical reasons.

As part of discharging our regulatory roles and responsibilities, Ofcom offer advice and assistance and where necessary undertake to investigate specific cases of interference to radio communications reported by stakeholders.

Can Ofcom take action in specific cases of interference?

The Wireless Telegraphy Act 2006 provides a mechanism for taking enforcement action to stop interference from specific classes of apparatus, for example a boiler thermostat, domestic appliance or a discharge light. This does not include PLT or similar classes of apparatus.

We are currently considering our ability to make a statutory instrument under section 54 of the Wireless Telegraphy Act 2006 which might give us scope to demand cessation where there were threats to public health, safety or other similar problems arising from harmful interference.

However it remains the case that the use of such powers, should they be provided, would not be "automatic". It would be necessary to show that such action was evidence based, considered proportionate and reasonable. In many of the types of interference cases reported to Ofcom by radio amateurs and shortwave listeners it is not clear that these tests would be met.

Current statistics on PLT complaints

Ofcom has maintained statistics on PLT since July 2008. As of December 2013 there have been a total of 289 reports of interference attributed to PLT. Every report of interference concerns an inability to receive a transmission on the shortwave band and is made by amateur radio users.

Complaints of PLT interference have shown considerable decline. Since January 2012, 2 complaints have been identified as PLT related (compared with 287 between July 2008 to December 2011). This is against an increased take-up of the technology.

The BBC and interference

The BBC Charter makes them responsible for the investigation of electro-magnetic interference to domestic radio and television reception. https://faq.external.bbc.co.uk/templates/bbcfaqs/emailstatic/interferencePage