Well, after trying two ultrasonic devices with no change whatsoever I'm not enclined to try another one, but thanks anyway. Right now Ruger is quietly sitting behind my head on the sofa, and he's usually very quiet.
After posting this I started doing a lot of research on collars, and most places say all collars are safe, and I would put the collar on myself before putting it on Ruger. However, there are stories of dogs getting shock collars and actually getting hurt, and some being so frightened it took a long time to get over it. That's why I'm asking other Yorkie owners what they think. There has to be a small, safe Yorkie-size bark collar that works. I've been looking at PetSafe collars.
Static - PetSafe Brand Official Website