3-36 B30 Bus Differential System GE Multilin3.3 DIRECT INPUT AND OUTPUT COMMUNICATIONS 3 HARDWARE3.3.8 IEEE C37.94 INTERFACEThe UR-series IEEE C37.94 communication modules (modules types 2G, 2H, 76, and 77) are designed to interface withIEEE C37.94 compliant digital multiplexers or an IEEE C37.94 compliant interface converter for use with direct input andoutput applications. The IEEE C37.94 standard defines a point-to-point optical link for synchronous data between a multi-plexer and a teleprotection device. This data is typically 64 kbps, but the standard provides for speeds up to 64n kbps,where n = 1, 2,…, 12. The UR-series C37.94 communication modules are either 64 kbps (with n fixed at 1) for 128 kbps(with n fixed at 2). 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:.• IEEE standard: C37.94 for 1 128 kbps optical fiber interface (for 2G and 2H modules) or C37.94 for 2 64 kbps opti-cal fiber interface (for 76 and 77 modules)• Fiber optic cable type: 50 mm or 62.5 mm core diameter optical fiber• Fiber optic mode: multi-mode• Fiber optic cable length: up to 2 km• Fiber optic connector: type ST• Wavelength: 830 ±40 nm• Connection: as per all fiber optic connections, a Tx to Rx connection is requiredThe UR-series C37.94 communication module can be connected directly to any compliant digital multiplexer that supportsthe IEEE C37.94 standard as shown below.The UR-series C37.94 communication module can be connected to the electrical interface (G.703, RS422, or X.21) of anon-compliant digital multiplexer via an optical-to-electrical interface converter that supports the IEEE C37.94 standard, asshown below.The UR-series C37.94 communication module has six (6) switches that are used to set the clock configuration. The func-tions of these control switches are shown below.
