ATM was originally designed to be used on fiber optic
networks.  Newer versions may be used with copper wire.  Category 5 (twisted pair) can be used, but it requires four pairs at 155 Mbps, in a 100% pure environment (no punch-down blocks or jumpers, no electronic radiation.)  There are two versions of ATM, one at 25.6 Mbps for interface with PCs or Workstations, the other at 155Mbps for network servers and high end workstations.  In general, ATMs are designed for use with PCI and SBus products.