Black Box Async RS232 Extender over Fiber - DB25 Male, ST MultimodeExtend Async RS232 data well beyond the usual 50 foot limit by using multimode fiber with the Black Box Async RS232 Extender. This rugged, point to point solution delivers reliable serial communication at data rates up to 76. 8 kbps over fiber distances up to 2. 5 miles (4 km). Designed for industrial environments and remote telemetry, it preserves the integrity of your serial signals while removing the constraints of copper cabling. The unit features