Black Box Async RS232/RS422/RS485 Fiber Extender ST Singlemode

The Black Box MD650A-13 is a fiber extender that carries asynchronous RS232, RS422, and RS485 signals over single-mode fiber fitted with ST connectors. It gives you a straightforward way to link control systems, sensors, PLCs, or any serial-based equipment when copper cabling is limited by distance or electrical noise.

Because the unit accepts all three major serial protocols, it lets you mix legacy RS232 devices with newer RS422 or RS485 gear on the same fiber run. The built-in protocol conversion removes the need for separate converter boxes, which simplifies wiring and reduces points of failure.

When speed matters, the extender can move RS422 or RS485 data at up to 10 Mbps and RS232 traffic at up to 200 kbps. Single-mode optics stretch those signals as far as 21.75 miles, making the module a reliable choice for sprawling campuses, refinery sites, or remote pumping stations where serial links must reach well beyond the limits of copper.

The fiber link also isolates equipment from ground loops and electromagnetic interference, a common concern on factory floors and near heavy machinery. By placing noisy equipment on one side of the fiber and sensitive controllers on the other, you gain a cleaner, more stable data path.

Setup stays simple. Terminal block connectors handle the serial wiring, and standard ST jacks take care of the fiber. The enclosure measures roughly 1.3 inches high, 3.5 inches wide, and 4 inches deep, so it tucks easily into control panels or DIN-rail shelves without crowding other gear.

Whether you are extending a single sensor, building a multipoint SCADA network, or retrofitting older RS232 devices into a modern automation system, this extender offers the reach, speed, and electrical isolation you need with the minimal hardware required.

• Works with RS232, RS422, and RS485 devices and converts protocols end-to-end
• Supports point-to-point links and multipoint networks
• Data rates up to 10 Mbps on RS422 or RS485, and up to 200 kbps on RS232
• Single-mode fiber range up to 21.75 miles (35 km)
• Operates in simplex, full-duplex, or half-duplex modes as the application requires
• Uses ST fiber connectors and a terminal block for serial wiring
• Compact housing measures 1.3 in H × 3.5 in W × 4 in D