I used to install T1s back when they were the "fast" way to get online. The vast majority of installations used HDSL to modulate the T1 onto the local loops. H

I used to install T1s back when they were the "fast" way to get online. The vast majority of installations used HDSL to modulate the T1 onto the local loops. HDSL powered the remote card from the one in the central office, using (IIRC) 130VDC. One time I was at a customer prem troubleshooting an installation. The customer's phone vendor was out there with me as we were hunting for the right cable pairs in the terminal. I was getting ready to call another tech back at the CO to put a tone generator on the line when the phone system vendor told me to just run my fingers across the terminals until I got a shock. I thought he was joking. He wasn't. He looked at me like I was a weenie and went ahead and did it himself. Dragged his fingers down the line until I saw him twitch. "Binding posts 47 and 48, right there" I had accidentally shocked myself probably dozens of times, but never as a troubleshooting technique!