3-34 T60 Transformer Protection System GE Multilin3.3 DIRECT INPUT/OUTPUT COMMUNICATIONS 3 HARDWARE3• Loop Timing Mode: The system clock is derived from the received line signal. Therefore, the G.703 timing selectionshould be in loop timing mode for connections to higher order systems. For connection to a higher order system (UR-to-multiplexer, factory defaults), set to octet timing (S1 = ON) and set timing mode to loop timing (S5 = OFF and S6 =OFF).The switch settings for the internal and loop timing modes are shown below:e) G.703 TEST MODESIn minimum remote loopback mode, the multiplexer is enabled to return the data from the external interface without anyprocessing to assist in diagnosing G.703 line-side problems irrespective of clock rate. Data enters from the G.703 inputs,passes through the data stabilization latch which also restores the proper signal polarity, passes through the multiplexerand then returns to the transmitter. The differential received data is processed and passed to the G.703 transmitter moduleafter which point the data is discarded. The G.703 receiver module is fully functional and continues to process data andpasses it to the differential Manchester transmitter module. Since timing is returned as it is received, the timing source isexpected to be from the G.703 line side of the interface.Figure 3–37: G.703 MINIMUM REMOTE LOOPBACK MODEIn dual loopback mode, the multiplexers are active and the functions of the circuit are divided into two with each receiver/transmitter pair linked together to deconstruct and then reconstruct their respective signals. Differential Manchester dataenters the Differential Manchester receiver module and then is returned to the differential Manchester transmitter module.Likewise, G.703 data enters the G.703 receiver module and is passed through to the G.703 transmitter module to bereturned as G.703 data. Because of the complete split in the communications path and because, in each case, the clocksare extracted and reconstructed with the outgoing data, in this mode there must be two independent sources of timing. Onesource lies on the G.703 line side of the interface while the other lies on the differential Manchester side of the interface.Figure 3–38: G.703 DUAL LOOPBACK MODE842752A1.CDRDMRDMXG7XG7RDMR = Differential Manchester ReceiverDMX = Differential Manchester TransmitterG7X = G.703 TransmitterG7R = G.703 Receiver842774A1.CDRDMRDMXG7XG7RDMR = Differential Manchester ReceiverDMX = Differential Manchester TransmitterG7X = G.703 TransmitterG7R = G.703 Receiver842775A1.CDR
