3-34 G60 Generator Management Relay GE Multilin3.3 DIRECT INPUT/OUTPUT COMMUNICATIONS 3 HARDWARE33.3.9 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 and/or IEEE C37.94 compliant interface converters that have been converted from 820 nm multi-mode fiber optics to 1300 nm ELED single-mode fiber optics. The IEEE C37.94 standard defines a point-to-point optical linkfor synchronous data between a multiplexer and a teleprotection device. This data is typically 64 kbps, but the standardprovides for speeds up to 64n kbps, where n = 1, 2,…, 12. The UR-series C37.94SM communication module is 64 kbpsonly with n fixed at 1. The frame is a valid International Telecommunications Union (ITU-T) recommended G.704 patternfrom the standpoint of framing and data rate. The frame is 256 bits and is repeated at a frame rate of 8000 Hz, with a result-ant bit rate 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 fiberFiber optic mode: single-mode, ELED compatible with HP HFBR-1315T transmitter and HP HFBR-2316T receiverFiber optic cable length: up to 10 kmFiber optic connector: type STWavelength: 1300 ±40 nmConnection: 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.For the Looped Timing Mode, the system clock is derived from the received line signal. Therefore, the timing selectionshould be in Loop Timing Mode for connections to higher order systems.The C37.94SM communications module cover removal procedure is as follows:842753A1.CDR
