newbie here on the site, question about PC Sync. I think I understand the principle of what it does, especially with digital cameras, of film camera with batteries in them. Weird/possibly dumb question. How does a large format lens physically/electronically send a signal to PC Sync cord that sends it to the flash, as what is the power source??

..if i do understand correctly the PC Sync sends a small current/voltage to the flash???, where does this current/voltage come from on a large format lens??

any clarifications would be helpful.