B&B Electronics FOSTCDR RS-232/RS-485 to Multimode Fiber Optic Converter 4km

B&B Electronics FOSTCDR RS-232/RS-485 to Multimode Fiber Optic Converter 4km

The B&B Electronics FOSTCDR is an industrial-grade serial to multimode fiber optic converter that bridges RS-232 and RS-485/422 serial equipment over fiber optic cable at distances up to 2.5 miles (4 km). It supports both point-to-point and multi-drop topologies, allowing one serial master to communicate with up to 31 devices around a fiber optic ring. The unit mounts on standard DIN rail and is configured via an 8-position DIP switch with screw terminal block wiring.

Specifications & What's Included

• Model: FOSTCDR
• Manufacturer: B&B Electronics Manufacturing Company
• Type: Industrial Serial to Multimode Fiber Optic Converter
• Supported Serial Interfaces: RS-232 (TX/RX), RS-485 (full/half duplex), RS-422
• Fiber Type: Multimode
• Fiber Connectors: ST — RX and TX ports on end panel
• Maximum Data Rate: 115.2 kbps
• Range: 2.5 miles (4 km)
• Input Voltage: 10–30 VDC (two separate power terminal positions: F and J)
• Isolation: 2000V
• Protocol Compatibility: MODBUS ASCII/RTU
• EMI/RFI Protection: Yes — inherent to fiber optic transmission medium
• Multi-Drop Capability: Up to 31 devices on a fiber optic ring
• RS-232 Mode: Supports transmit and receive data; handshaking signals not passed through
• RS-485 Auto Send Data Control: Automatic driver control eliminates need for special software
• Configuration: 8-position DIP switch (baud rate: >57.6k, 38.4k, 19.2k, 9600, 4800; RS-485 Off/422; Repeat Fiber; HD Off / FD modes)
• Terminal Blocks: (A) RS-232 RD, (B/C) GND, (D) RS-232 TD, (E) No Connect, (F/J) 10–30 VDC, (G) RS-485 TD A(−), (H) RS-485 TD B(+), (K) RS-485 RD A(−), (L) RS-485 RD B(+), (M) GND
• LED Indicators: RD (receive data), TD (transmit data), Power
• Mounting: DIN rail
• Certifications: UL (E222870), CE, FCC Part 15
• Manufacture Date: March 2011 (per label)
• Included: Converter unit only

Applications

Serial-to-fiber converters like the FOSTCDR are used in industrial automation and process control environments where serial devices — PLCs, RTUs, HMIs, sensors, and SCADA equipment — need to communicate over longer distances than copper serial cabling allows, or in electrically noisy environments where EMI/RFI immunity is critical. The fiber optic link eliminates ground loop issues and provides inherent galvanic isolation (2000V here), making it well-suited for installations across separate electrical grounds such as between buildings or across a plant floor. MODBUS ASCII/RTU compatibility makes the FOSTCDR a natural fit for existing MODBUS networks, allowing serial MODBUS masters to reach remote slave devices via fiber. The multi-drop ring topology extends the unit's usefulness in multi-node networks, such as distributed I/O or remote terminal unit (RTU) installations. B&B Electronics — now operating as Advantech B+B SmartWorx — has produced this class of DIN-rail industrial serial converter since the 1990s; units like the FOSTCDR remain in service in legacy industrial control systems and are actively sought for maintenance, expansion, and replacement in those installations.