The FRM220-FXO-FXS-SC02B is a POTS (RJ11) port over fiber optic media converter. The PSTN two-wire POTS telephone port can be configured either as an FXO (PBX trunk) or FXS (telephone set/fax machine/dial-up modem) device just by a simple DIP switch setting. Using a pair of converters, a telephone line can be extended over a fiber optic circuit, providing full service and features like Caller ID. The converter can be used in service mode, alowing connection of 2 telephone sets in between. FRM220-FXO-FXS-SC02B operates on multimode fiber up to 2Km (1.3mi) distance and it is using a SINGLE STRAND of multi-mode fiber, either 62.5/125um or 50/125um. The fiber media converter has only one SC type optical connector and does the BiDirectional communication using Tx: 1310nm and Rx: 850nm wavelengths. An FRM220-FXO-FXS-SC02B must be paired with FRM220-FXO-FXS-SC02A model, which is acting complementary over the fiber, using Tx: 850nm and Rx: 1310nm. The BiDirectional model is saving precious strands of fiber for very little price difference. When fiber is scarce, using a BiDirectional model will halve the fiber requirements while providing absolutely same performance as a dual strand model. When the FRM220-FXO-FXS-SC02A (or B) POTS over fiber converter is placed in the FRM220 rack with in-band and SNMP management, the converters status, type, version, fiber link status, POTS RJ11 port status and alarms can all be displayed. Configuration is also available to enable or disable the port, reset the port, do far end fault setting, and initiate local or far end loop-back tests.