The PXM1E is a Private Network-to-Network Interface (PNNI)-enabled, double-height switch controller that provides switching capabilities for use at the ATM network edge. The PXM1E contains the processing intelligence, controls the Cisco MGX switch, and supports external interfaces for user access and NNI/UNI ports.The PXM1E is part of a card set that consists of a PXM1E, a user interface back card, and an NNI/UNI port back card. The switch can support up to two card sets.One PXM1E user interface back card (PXM-UI-S3 or PXM-UI-S3/B) provides management interfaces for configuring the switch, using external clocks, and triggering external alarms. The user interface back card is installed in the top bay of the switch (when the switch is viewed from the rear) behind the PXM1E.