CHAPTER 3: INSTALLATION DIRECT INPUT AND OUTPUT COMMUNICATIONSN60 NETWORK STABILITY AND SYNCHROPHASOR MEASUREMENT SYSTEM – INSTRUCTION MANUAL 3-313Figure 3-38: RS422 and fiber interface connectionThe connections shown in the figure are for multiplexers configured as data communications equipment (DCE) units.3.4.8 IEEE C37.94 interfaceThe UR-series IEEE C37.94 communication modules (module types 2G, 2H, 2I, 2J, 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 amultiplexer 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 (withn fixed at 2). The frame is a valid International Telecommunications Union (ITU-T) recommended G.704 pattern from thestandpoint 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 kbpsoptical fiber interface (for 76 and 77 modules)• Fiber optic cable type — 50 mm or 62.5 mm core diameter optical fiber• Fiber optic mode — multimode• 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. The figure shows the concept.NOTICE When using a laser interface, attenuators can be necessary to ensure that you do not exceedmaximum optical input power to the receiver.Tx2 Rx2842777A2.CDR~8a7L, 7M, 7N,7P, and 74ShieldTx –Rx –Tx +Rx +RS422communications~4b~3a~3b~6a~2aRS422channel 1Surge+–~7a~8bClockchannel 1Common ~2bCOMFiberchannel 2UR-seriesdeviceIEEE C37.94fiber interfaceup to 2 km842755A2.CDRDigitalmultiplexer,IEEE C37.94compliant
