3 ms·

They are not empty. Very much necessary for fiber termination, relays, PoPs. Copper also is used.

• cm2187 5y ago
  But I thought a lot of these massive exchanges were built for the physical switching devices, which must have been completely miniaturised when they switched to digital.
  • jbledsoe2112 5y ago
    When they went digital they were downsized. But for the most part they're still there.