The pet corrector is a can of pressurised air - you use it to interupt unwanted behaviour such as barking, aggression or deerhound hassling
It does not hurt them in any way as it only emits a sharp, loud hissing noise when you aim it at them. It is very effective. I always take a can with me as it works to break up dog fights. I have a bit more peace of mind that if my dog come under attack (or, God forbid, launch their own attack) then i have the pet coorector to break it up.
If ASBO hound starts to rough the others up I only have to show him the can and he stops straight away.
You can get it from Pets at Home and most good pet shops and it costs about 5.99. It is in slim, red can and you also buy a holster for it so you can wear it on your waistband - I am not that cool - I keep the can in my pocket
I don't think it will help your mum though