The use of twisted pair cable for high speed LAN signalling necessitates the inclusion of transmit and receive magnetics to couple the transmission signal to and from the copper media The choice of magnetics in a given implementation can have a significant effect on the integrity of the transmission signal Several important factors must be considered when choosing the magnetics for FDDI twisted pair PMDs This application note discusses key performance parameters of magnetics suitable for use within a PMD designed for ANSI X3T9 5 FDDI Twisted Pair Draft Proposal compliance Although magnetics are required for both shielded and unshielded twisted pair media this note focuses specifically on magnetics suitable for FDDI signalling over Category 5 Unshielded Twisted Pair This note includes layout recommendations for a typical PMD transceiver implementation employing the National Semiconductor DP83223 TWISTER transceiver and suggests the use of some readily available magnetics