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Technical Documents

  • Oct

    Repetitive Electrical Impulse Noise (REIN)

    Author: Technical Support
    Server room from hell
  • REINRepetitive Electrical Impulse Noise (REIN) can be the cause of frequent loss of the adsl signal from the exchange, and it can also cause a broadband line to perform below its expected performance.

    What is EMI?

    ElectroMagnetic Interference is undesirable disturbance from electrical or electronic sources. Electronic equipment generates electro magnetic fields, that can cause interference with other electronic devices.

    There are also natural sources of EMI such as from the sun, the Northern Lights and of course thunder storms.

    What is RFI?

    Radio Frequency Interference is undesirable disturbance from electrical or electronic sources that interferes with radio frequency transmission. RFI can often be picked up by nearby wireless devices. I'm sure we've all heard the familiar buzz from mobile phones when near PC speakers.

    What's the difference between EMI and RFI?

    The two terms are often used interchangeably, but to be specific EMI is any frequency of electrical noise, whilst RFI is electrical energy produced in the same frequencies used by radio transmission.

    SHINEWhat is SHINE?

    SHINE (Single High level Impulse Noise Event) is a single brief burst of noise.

    The noise burst will show as a single sharp spike on graphing tools. Generally these types of noise bursts will cause line errors such as CRCs or errored seconds and may go un-noticed, but they can be sufficient to knock a broadband connection out completely causing the line to resync.

    What causes SHINE?

    SHINE is usually the effect of turning on or off of an electrical device at the mains. Sometimes you may hear an audible 'pop' or 'crackle' when the switch is flicked.

    If there is a pattern to the times check that they don't coincide with something such as lighting or central heating timers or thermostats. The adsl connection will normally be perfectly fine with flat SNRm at all other times.

    What is REIN?

    REIN is when interference from an external power source interferes with the adsl broadband (or other telecommunications) signal. Usually the two should coincide happily and cause no problems, however on occasions an electrical item can introduce additional noise in the same band of frequencies utilised by DSL. This noise then drowns out the strength of the adsl signal, either causing degradation of achievable speed or even total loss of synchronisation with the exchange.

    Whilst all electrical equipment will generate some sort of noise, it should comply with the Electromagnetic Compatibility (EMC) Directives and avoid generating electromagnetic disturbance utilised by radio and telecommunications equipment, but some equipment may either be old, foreign or faulty, any of which can be the source of some DSL broadband problems.

    How do I know if my fault is attributable to REIN?

    Tracking down REIN faults can prove tricky, and quite often it is down to us the user to diagnose these faults. Whilst BT special faults do have sophisticated equipment to help track down this type of fault, it should be remembered that REIN faults aren't always within BT's remit as it is outside their control.
    REIN faults are also more common outside of working hours when more people are at home, turning on and utilising electrical equipment etc.

    Most cases are found by careful observations of conditions on their line by careful monitoring of what times the line deteriorates and trying to tie this up with the timing of power sources being switched on.

    Monitoring your SNR margin from your router linestats should provide extremely helpful insight as to when these problems occur. See below for some tools to aid SNR monitoring.

    Typical REIN sources

    This list is not exhaustive but known and common culprits are:

    Faulty thermostats (Central heating, Immersion heaters).
    Electrical power supply units (Laptops, Routers, Plasma, TVs).
    Decorative electrical items (Christmas tree lights, Touch lights).
    Digital Communication Receivers (Satellite and Freeview set top boxes).
    Security systems (PIR lights switching on and off).
    Fluorescence Lights & Faulty Street Lights
    Powerline Adapters & Treadmills
    Industrial/Commercial power usage (Electric Railways, Electric fences, Electric motors).
    Internal power cables and telecom cables running close together.
    A current imbalance between two power carrying conductors (Earth leakage fault).

    What is PEIN?

    PEIN is Prolonged Electrical Impulse Noise. PEIN is defined as non repetitive impulse noise events that have a duration between 1ms and 10ms. Although described as non repetitive it can appear as random bursts with no fixed inter-arrival times.

    REIN, SHINE & PEIN Summary

    Impulse Noise Repetitive? Burst Length Effects
    REIN Yes.  Fixed intervals <1 ms Variable SNR, Bit Errors.
    PEIN Random bursts 1 - 10 ms SNR spikes, Bit Errors
    SHINE No > 10 ms High CRCs/Loss of Sync

    Is there anything I can do to try track down & identify the source of REIN?

    If you suspect there is something interfering with your broadband, get an AM/MW radio and tune it to 612KHz.

    If you hold the radio next to an LCD screen for your PC as an example you would hear a distinct noise. This should fade away if you move the radio a quarter to half a meter away. Hold it by your modem/router and you'll hear the DSL signal.

    REINIf you get a distinct noise enveloping a larger area, then this may be picked up by your router causing an SNR problem (or even drop of sync). By using the radio you may be able to get an idea of where the noise is coming from. Switch the suspect appliance off & retest your DSL broadband connection. By distinct noise you're looking for a clear buzz, whistle, clicking etc. White noise or a general shhhhh noise is less likely to be the cause of the problem, same as any radio broadcast. (In the south of the UK you may hear a French radio station from around 612KHz.)

    Be aware that any noise heard on the radio is not always affecting your DSL connection, and you may still have REIN issues in the area which will not be picked up @ 612Khz as REIN is often notoriously difficult to pin-point. This method can be a bit hazy so don’t rely on it completely by any means.

    Xmas lights are a classic cause, as are noisy electrical appliance with a long length of wire which acts as an antennae. Sometimes you can cure it with a ferrite sleeve (that small cylindrical thing you normally see along your monitor cable which doesn't’t seem to do anything) which you can get from electrical suppliers such as Maplin.

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