GE L90, Инструкция по эксплуатации

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3-40 L90 LINE CURRENT DIFFERENTIAL SYSTEM – INSTRUCTION MANUAL
PILOT CHANNEL COMMUNICATIONS CHAPTER 3: INSTALLATION
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criteria must be followed since there is one clock input for the two RS422 channels. The system functions correctly when
the following connections are observed and your data module has a terminal timing feature. Terminal timing is a common
feature to most synchronous data units that allows the module to accept timing from an external source. Using the
terminal timing feature, two-channel applications can be achieved if these connections are followed: the send timing
outputs from the multiplexer (data module 1) connects to the clock inputs of the UR RS422 interface in the usual way. In
addition, the send timing outputs of data module 1 are also paralleled to the terminal timing inputs of data module 2. By
using this configuration, the timing for both data modules and both UR RS422 channels are derived from a single clock
source. As a result, data sampling for both of the UR RS422 channels is synchronized via the send timing leads on data
module 1, shown as follows. If the terminal timing feature is not available or this type of connection is not wanted, the
G.703 interface is a viable option that does not impose timing restrictions.
Figure 3-42: Timing configuration for RS422 two-channel, three-terminal application
Data module 1 provides timing to the L90 RS422 interface via the ST(A) and ST(B) outputs. Data module 1 also provides
timing to data module 2 TT(A) and TT(B) inputs via the ST(A) and AT(B) outputs. The data module pin numbers have been
omitted in the figure because they vary by manufacturer.