3-42 B30 Bus Differential System GE Multilin3.3 DIRECT INPUT AND OUTPUT COMMUNICATIONS 3 HARDWARE3The UR-series C37.94SM communication module has six switches that are used to set the clock configuration. The func-tions 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:1. Remove the C37.94SM module (modules 2A or 2B):The ejector/inserter clips located at the top and at the bottom of each module, must be pulled simultaneously in orderto release the module for removal. Before performing this action, control power must be removed from the relay.The original location of the module should be recorded to help ensure that the same or replacement module is insertedinto the correct slot.2. Remove the module cover screw.3. Remove the top cover by sliding it towards the rear and then lift it upwards.4. Set the timing selection switches (channel 1, channel 2) to the desired timing modes (see description above).5. Replace the top cover and the cover screw.6. Re-insert the C37.94SM module. Take care to ensure that the correct module type is inserted into the correct slotposition. The ejector/inserter clips located at the top and at the bottom of each module must be in the disengaged posi-tion as the module is smoothly inserted into the slot. Once the clips have cleared the raised edge of the chassis,engage the clips simultaneously. When the clips have locked into position, the module will be fully inserted.842753A1.CDR
