A fieldbus segment acts as a transmission line for data communications between the various devices. A terminator balances the impedance at each end of a transmission line to ensure reliable communications. The H1 card requires an external terminator for each segment as well as a second terminator at the device end of the segment. Some fieldbus power supplies and device connection blocks may provide a fixed or switchable terminator for one end of the segment. The H1 with Integrated Power card contains an integrated terminator for each segment. A second terminator is required at the field end of each segment. Ensure that each segment is terminated in two places.