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Broadband: Understanding REIN and SHINE

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Broadband: Understanding REIN and SHINE

What are REIN and SHINE?

Repetitive Electrical Impulse Noise (REIN) and Single Isolated Impulse Noise (SHINE) describe interference that can affect the stability and performance of a Broadband service. In both cases, a power source is generating interference in the frequencies used by the ADSL Broadband service.

REIN is where this interference is generated for the duration of use of an electrical device, and will typically result in disconnections or line errors while the device is in use. At its most extreme, REIN may prevent any connection being established at all.

SHINE is where this interference is generated as a burst – when a device is powered on or off, for example. As a result disconnections or line errors may result at the time a device is switched on or off.

What are the effects of REIN and
SHINE on my Broadband service?

In addition to the disconnections caused by REIN or SHINE you are likely to see a slower speed due to line errors and BT’s automated systems working to counteract the symptoms by restricting the maximum speed you can connect at. Lowering the speed creates a “buffer” to the interference, so it doesn’t cause your connection to drop.

Example causes of REIN and SHINE

Many electrical devices could be responsible for causing REIN and SHINE that affects your Broadband service. Below is a list of some example sources, however many electrical devices have the potential to cause REIN or SHINE:

  • Faulty power adapters.
  • Timed devices, such as central heating.
  • Christmas tree lights (especially on ‘flash’ setting).
  • EPOS and PDQ devices.
  • Railway power lines.
  • Street lights.
  • Roadworks.
  • Faulty set-top boxes, televisions and other appliances.
  • Power cables running close to telephone wiring in the home.

How can I identify REIN or SHINE and
reduce the effect on my Broadband service?

In the vast majority of cases, the source of interference will be within your own home or business premises. As a starting point, you should ensure your Broadband equipment is connected to an ADSL filter at the BT Master Socket – the socket through which the telephone line enters your premises. Internal wiring can act as an antenna to interference, so eliminating or reducing the length of internal wiring will do a lot to minimise the effects of REIN or SHINE.

An alternative to switching devices off is to use an AM/MW radio tuned to 612Khz - this video shows you how this method works:


To find the cause of interference is a process of elimination, once you’ve optimised the physical set up of your equipment look for patterns in when problems occur and determine what device is powered on or becomes active at those times. If you can’t locate any single source power off all electrical devices and switch them on one-by-one, monitoring for the symptoms of interference until you find a source.

If no devices in your premises appear to be causing interference then you will need to look further afield. It is possible equipment of your neighbours’ is causing interference, or there could be a source along the route the telephone line takes from the BT exchange to your premises. If this is the case other people are likely to be experiencing the problems too, so noting the times and days this happens will be useful for determining a potential source (e.g. if the cause is a piece of equipment at a business problems may only occur on weekdays when they are open for business).

If the source is external, but can’t be located and eliminated through talking to your own neighbours, then a fault can be reported to BT by us (and your neighbours should make a report to their Broadband providers too). It is important to note that investigations can be complicated and take many months in some cases, and sometimes ultimately the cause cannot be eliminated. This is because the cause will likely be outside of BT’s control and will require specialist engineers to locate it.

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