When ding dongs go wrong

01 August 2017

    Ofcom engineers recently came to the rescue of drivers who couldn’t get into their cars because of a faulty doorbell.

    If you found your key fob wasn’t working and couldn’t get into your car, you’d probably call a mechanic - but what if other people in your street were having the same problem? Would you think of calling Ofcom?

    That’s what Wendy Macbean from Derry/Londonderry did recently, when she and others had this problem outside her gym on the city’s Spencer Road. We took the call at our Belfast office on a Friday afternoon and reported it to Ofcom’s Spectrum Management Centre in Baldock.

    The following Monday, they despatched two Ofcom engineers – Stuart Lannie and Robert Barfoot (our recently recruited apprentice) – to investigate.

    Wendy told our engineers how customers at her gym and other nearby businesses had, on and off, for nearly two weeks been unable to lock and unlock their cars. One older woman had become quite distressed when she was locked out of her car for more than an hour, while Wendy had resorted to not locking hers any more.

    Our engineers broke out their spectrum analyser – a clever piece of kit that scans the airwaves and detects anything out of the ordinary. On this occasion it didn’t, but they asked Wendy to keep a log. Sure enough, the problem reoccurred and Stuart and Robert went back to Derry/Londonderry the following Monday and were more successful.

    Again, using their trusty spectrum analyser, they traced the problem to a particular bit of the electro-magnetic spectrum – 433.92 Mhz. This is a licence-exempt part of the Ultra High Frequency (UHF) spectrum known as the short-range device frequency.

    And the kind of devices that use it are things like car key fobs, oil watchmen (that tell you when your heating oil is running low), and remote controls used by building site crane operators.

    “For the most part, these devices are only used in short bursts,” explains Robert.

    “The problem comes when one of these becomes faulty and they remain on permanently. When that happens, they can interfere with other nearby devices, like car key fobs, using those same radio waves, which is what happened here.”

    They traced the problem to premises nearby. Once inside, they quickly found the cause of the problem – a faulty wireless doorbell. It was switched off and normal service was resumed for motorists out on the street.