The Allen-Bradley Foundation Fieldbus Linking Device that is known as the 1757-FFLD4 Linking Device is an electronic device that provides a connecting interface for interacting with a Foundation Fieldbus network, which is a digital, two-way, serial communication system used in process plants and power plant applications worldwide. The Allen-Bradley 1757-FFLD4 Foundation Fieldbus Linking Device allows for connections with up to 4 different FOUNDATION Fieldbus H1 networks, and for operating at 31.25 kbps speed. Each H1 network can accommodate up to 16 field devices/host systems, but for the optimal operation of the system, the recommendation is to connect only 8 or 10 devices per network.

The Allen-Bradley 1757-FFLD4 Foundation Fieldbus Linking Device needs to be supplied with a 24 Volts DC (± 20%) voltage level. Its recommended current rating is 300 milliamps, with an inrush current of 1.5 Amps. Because these linking devices are supplied in an open type construction style, it is necessary prevent direct contact with water, dirt, moisture, or other related contaminants. Installing the Allen-Bradley 1757-FFLD4 Foundation Fieldbus Linking Device with a DIN rail inside a NEMA Type 4/12 enclosure will help extend its lifespan. The DC power wiring connections must be made with 0.2 or 1.5 millimeters square (26 or 16 AWG) stranded copper wires. For Fieldbus connections, 0.8 millimeters square (18 AWG) solid or stranded shielded twisted-pair copper wires are the best options. Ethernet connections should be made using RJ45 connectors according to the IEC 60603-7, 2, or 4-pair Category 5e minimum cable according to the TIA 568-B.1 standards or Category 5 cable according to the ISO/IEC 24702 standards.