Calm has been restored!
Our vet advised we purchase a couple of these as our older cat has started to leave us "little messages" outside his litter tray. She thought there might be a behavioural problem. Sadly, the plug-ins haven't sorted that out, we're still investigating. However, the two cats DO share a home with a Boston Terrier and, while the breed is known for its love of other animals, there ARE occasions when the atmosphere is a tad fraught! The cats, particularly the old boy, appear more chilled out!