The MODEL 277SM was designed to provide the most versatile connection possible between any asynchronous serial equipment using Fiber Optic cable. It allows any two pieces of asynchronous serial equipment to communicate full or half-duplex over two fibers at typical distances up to 20KM. The converter can also be set up in "Repeater" mode to create a multi-drop master/slave configuration, allowing one serial device to talk to multiple slave devices around a fiber ring.

RS-232 data signals at up to 115.2K bps and RS-422, or RS-485 data signals at up to 115.2K bps are supported. Different standards can be mixed and matched to allow RS-232 devices to connect to your RS-422 or RS-485 system. This means the MODEL 277SM can replace converters and isolators when connecting remote devices, while providing the EMI/RFI and transient immunity of optical fiber.

The MODEL 277SM supports both the Transmit and Receive data lines, and provides full hardware control of the RS-422 /485 driver with automatic Send Data Control circuit. Timeouts are auto detect between 0.10 and 2.2 ms. All serial connections are provided on the DB-9 female connector or 6-bit terminal, while the single-mode fiber is connected via two SC connectors. The unit is powered by 9VDC at 140 mA max.