I've noticed here and there that the people servicing my A/C and Heating system as well as the power company guys all seem to show up with this wizbang multi-meter that has an attachment that can just collar an insulated wire and read it.
I honestly don't remember if they were testing nominal voltage, or current flow, or if one or the other is impossible.
Are such things available inexpensively? There are many times when working with house (and car!) wiring that I really would bennefit from reading the characteristics of a line without breaking into it.
Thanks!