Model 9PFLST allows any two pieces of RS-232 asynchronous serial equipment to communicate full-duplex over two multi-mode fibers. Typical distances up to 2.5 miles (4 km) are possible with no external power required. The 9PFLST supports both data signals at up to 115.2 kbps as well as the RTS/CTS handshake lines. This means the 9PFLST can replace short haul modems and isolators when connecting remote devices, while providing the EMI/RFI and transient immunity of optical fiber.

RS-232 connections are provided on the same DB9 female connector, while the multi-mode fiber is connected via two ST connectors. The unit is port powered by the RS-232 Transmit Data and handshake lines. When handshake lines are not available, or when using a low power RS-232 port, the 9PFLST can be powered by an external 12VDC supply, drawing 50 mA maximum.