The NYC MTA is upgrading to communications-based train control but the majority of the system still uses electro-mechanical relay switches and other technology from the 1930s to run today’s subway system. And some of the cabling is the original cloth-covered cabling.
Here’s a video on YouTube for a look at this underground system.
[As my brother and father were quick to point out both truthfully and comically, there are advantages to this antiquated system: no buggy software upgrades or remote hacking.]
via Laughing Squid