When I was a burglar alarm installer, my central office (CO) had a type of alarm system which used 130 volt DC. The CO would send out 130 VDC and it would run through the BA system and the CO would be able to tell if the negative side or the positive side of the alarm was broken. Anyway, when we got to the job site, we would have to get the telco guys to find our "BA" line. One day this guy was looking for our BA line by touching his tongue with a piece of wire and touching the telco terminals. We tried to warn him several times by reminding him that it was a BA line. When he found it, he let out a very loud scream and asked us what was on that line. That was when my partner told him that it was 130 VDC. He never looked for a BA line again that way.
