Analogue TV – Electrical interference

Electrical interference can cause ragged horizontal patterns, random white dots or flashes on the TV picture, or buzzes and clicks on the sound.

The interference can be caused by anything powered by electricity, such as domestic appliances, switches and computers (in your home or a near neighbour's). The most common cause is a faulty boiler or central heating thermostat, which can lead to regular bursts of interference (e.g. for 10 seconds every 20 minutes).

Sometimes, high-voltage electrical equipment outside your home can cause interference.

An unusual colour effect on the TV screen may be caused by the magnets inside a hi-fi speaker, so don't put speakers on or near the TV.

• To work out what is causing the interference, leave the TV on and switch off or disconnect your electrical appliances one at a time to see if it stops. You may need to repair or replace a faulty appliance or thermostat.
• If you're getting an unusual colour effect on the screen, make sure there are no hi-fi speakers on or near the TV.
• If you think high-voltage electrical equipment outside your home may be causing the interference, you could ask Ofcom to investigate - but please note that Ofcom may charge a fee for this. See the Ofcom page about TV or radio interference or reception problems for more information.