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It all started on an unremarkable weekend two years ago. "I had the idea one weekend after my eldest son had left home and we just kept getting lots of calls for him," says Farrell. "It was really getting on my nerves but then I had an idea."
Within three hours of buying £2.60 worth of components he had built the prototype of the "Follow Me Phone".
"The invention is a fixed-line telephone that has its own telephone number built into it," explains Farrell. "It can be connected to any standard telephone socket and will then receive calls made to its number, regardless of its location.
"All calls made from it are charged to the owner of the phone rather than the line it is connected to and it will only ring if the incoming call is for that specific number."
When they hear about Follow Me Phone most people point out that they already have a mobile phone, but Farrell says they are missing the point.
"A land line is cheaper, has a good signal and is more comfortable to talk on for any length of time," he explains. "It is an alternative to the mobile."
Farrell works for a telecoms equipment manufacturer and some of his colleagues were able to help with the hardware, while Farrell concentrated on the exchange simulator software.
After a bit of convincing Farrell's bosses saw the benefits of the invention and agreed to try to sell it. The company now holds the patent, with Farrell acknowledged as the inventor. But it has struggled to get a service provider to take the idea on.
Farrell needed to reach a wider audience. The drive into work provided him with the solution. "I was listening to the local radio when I heard Trevor Baylis, the presenter of Best Inventions, talking about his show," he says.
BBC TV programme Best Inventions gets three inventors to pitch their ideas to a studio audience which then votes for the one they like best. The winner gets an introduction to a company that will try to take the idea forward.
"This got me thinking that I could have a go, so I sent in a two-line e-mail to the programme explaining about my invention."
The programme makers were interested and a researcher was dispatched to find out more. They decided to go with it and a while later a film crew arrived to put the phone through its paces.
"They tested the phone in the hotel where they were staying and a caller came through to the hotel switchboard. It was also tested in a hospital, where mobiles aren't allowed and using a call box can work out to be very expensive."
Farrell, who lives in Manchester, had to come to London to film the show. This was his first chance to see the other competitors. There was no danger of the three inventions getting muddled up. "I was up against a motorbike helmet with a built-in brake light and a tripod ladder which is supposed to be safer on unstable ground," says Farrell.
At the end of the show the audience pressed their buttons to vote for their favourite invention. Farrell was devastated to see that no one had voted for him.
However, it transpired that microphone interference had scrambled the voting system and only six votes had been registered.
The audience voted again, Farrell still came third but this time with a more respectable 15%. The motorbike helmet was the winner.
"Although I didn't win, something may come of the programme," says Farrell. "The idea is to get people thinking about how the invention could be useful to them."