GE Multilin L30 Line Current Differential System 3-373 HARDWARE 3.3 PILOT CHANNEL COMMUNICATIONS33.3.9 C37.94SM INTERFACEThe UR-series C37.94SM communication modules (2A and 2B) are designed to interface with modified IEEE C37.94 com-pliant digital multiplexers or IEEE C37.94 compliant interface converters that have been converted from 820 nm multi-modefiber optics to 1300 nm ELED single-mode fiber optics. The IEEE C37.94 standard defines a point-to-point optical link forsynchronous data between a multiplexer and a teleprotection device. This data is typically 64 kbps, but the standard pro-vides for speeds up to 64n kbps, where n = 1, 2,…, 12. The UR-series C37.94SM communication module is 64 kbps onlywith n fixed at 1. The frame is a valid International Telecommunications Union (ITU-T) recommended G.704 pattern fromthe standpoint of framing and data rate. The frame is 256 bits and is repeated at a frame rate of 8000 Hz, with a resultant bitrate of 2048 kbps.The specifications for the module are as follows:• Emulated IEEE standard: emulates C37.94 for 1 × 64 kbps optical fiber interface (modules set to n = 1 or 64 kbps).• Fiber optic cable type: 9/125 μm core diameter optical fiber.• Fiber optic mode: single-mode, ELED compatible with HP HFBR-1315T transmitter and HP HFBR-2316T receiver.• Fiber optic cable length: up to 10 km.• Fiber optic connector: type ST.• Wavelength: 1300 ±40 nm.• Connection: as per all fiber optic connections, a Tx to Rx connection is required.The UR-series C37.94SM communication module can be connected directly to any compliant digital multiplexer that sup-ports C37.94SM as shown below.It can also can be connected directly to any other UR-series relay with a C37.94SM module as shown below.The UR-series C37.94SM communication module has six (6) switches that are used to set the clock configuration. Thefunctions of these control switches is shown below.For the internal timing mode, the system clock is generated internally. Therefore, the timing switch selection should beinternal timing for relay 1 and loop timed for relay 2. There must be only one timing source configured.842753A1.CDR
