3-26 B30 BUS DIFFERENTIAL SYSTEM – INSTRUCTION MANUALDIRECT INPUT AND OUTPUT COMMUNICATIONS CHAPTER 3: INSTALLATION3Figure 3-24: Options for the IRIG-B connection3.4 Direct input and output communications3.4.1 DescriptionThe direct inputs and outputs feature makes use of the type 7 series of communications modules and allows directmessaging between UR devices. The communications modules are outlined in the table later in this section.The communications channels are normally connected in a ring configuration, as shown in the following figure. Thetransmitter of one module is connected to the receiver of the next module. The transmitter of this second module is thenconnected to the receiver of the next module in the ring. This is continued to form a communications ring. The figureillustrates a ring of four UR-series relays with the following connections: UR1-Tx to UR2-Rx, UR2-Tx to UR3-Rx, UR3-Tx toUR4-Rx, and UR4-Tx to UR1-Rx. A maximum of 16 URs can be connected in a single ring.Using an amplitude-modulated receiver causes errors up to 1 ms in event time stamping.
