Yep, 12V is "safe" but when you have a few hundred amps availible and ya' short across it, things kind of get a bit hot let alone all the 'pirty sparks.. Very easy way to say start your car---> on fire. ( seen it)
Telephone?? Get your buddy to work on it.. If they don't feel the 50V D.C present, CALL THEM... See if they feel the 90V A.C "ring" [Linked Image]