With the Thing in my pocket, I was John Wayne: Nicholas Roe uses high technology to vanquish two dangerous dogs but feels registration would be a better safeguard

We were settling down to watch a film when the trouble started. In our town, dogs usually have a distinctive tone and style when they cut loose - short yapping, instantly silenced by considerate neighbours. But this was different. It was deep, angry baying, and so persistent that you could not watch Kiss of the Spiderwoman over the top of it.

So we waited until irritation overcame delicacy, then went to the curtains and peered out. The details were clear in the light from a streetlamp: a young woman was circling warily outside a house just along the road, casting glances at a great dane and a big, black mongrel that stood just behind the gate and were barking at her like mad, literally like mad, on and on. Beyond the animals, the front door of the house stood wide open. As we watched, a woman from a nearby flat approached the circling girl, and they formed a lonely group, staring at the dogs, then back at each other, then at the rest of the empty road, then at the dogs.

I asked my wife: 'Should I go out?'

'What could you do?'

'I could take the Thing.'

She raised her eyebrows. I went down to the kitchen and rummaged in an old fruit bowl where we keep letters, coins, children's marbles, junk, and right at the bottom I found what I was looking for: a small, grey device like a shaver. I had never used it before, I did not even know if it worked; the truth is, I had almost forgotten about it until the dogs started barking.

Out of the front door, down the steps, into the street. The two women looked up. One said: 'I can't get in. I'm the lodger, but there's no one in and I tried, but the dogs won't let me . . . .'

'Would you like me to try?' I asked.

I felt like John Wayne. The women looked at me as if I were mad. But, of course, they did not know about the Thing in my pocket.

'Yes please,' said the lodger. I walked towards the dark gate, watching the dogs reach new levels of anger, their shapes unclear against the light of the open front door behind them, though you could pick out the shine of their teeth easily enough. I didn't feel like John Wayne any more, I felt like going home.

Close up, I pulled out the Thing, pointed, and pressed the trigger. Nothing. No sound, no movement, no bullet, no light except for a little red dot shining to show that it was working. The dogs stopped barking, pricked up their ears, ran back a few paces, then came back. I pressed again. This time, the great dane turned and fled to the top of the wide concrete steps that led to the front door, hesitating there in perplexed silence. Turning to the other animal, I did it again, with the same result.

The neighbour came up, looking puzzled. 'Ultra sound?' she said at last. I nodded, almost disappointed that she should have spotted the secret so soon, but it was not finished yet.

The lodger said she wanted to go in now but was still frightened, so we tried it together, very slowly opening the gate, stepping into the garden. At the bottom of the steps I fired again and the dogs backed off still farther. We went up, one by one. At the top I tried another burst and this time the animals fled into the house as if pursued by devils, running to a back room, where I shut them in with relief.

I turned to the lodger and said, 'It's OK.' Just like in the movies. She was grateful, I was stupidly proud. I went home feeling wonderful. Silly, of course. I happened to have written a piece about dog wardens two years ago and a man called Terry Singh, in charge of the council dog service in Bradford, gave me the Thing just in case. Terry thinks dogs should be registered, so do I.

The agreement was sealed in this gift, standard equipment for some handlers. It is called a Dazer and the sound it gives off is of such high frequency that only dogs can hear it. They do not like it, so they run away - a fact I knew in theory, and now in practice, too.

Going back indoors, I put the Dazer back in the fruit bowl and thought how glad I was that it had worked, how daft it was that we need such things, how maybe I could have used it to stop a rottweiler savaging a little girl, which would have been marvellous.

Then I gave up dreaming and decided I was simply glad that I didn't have to face scarey incidents like that every day, the way Terry Singh does.