Cabletron Systems 100BASE-FX, Руководство по кабельной продукции

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Ethernet Media
4-26 Connector Types
Figure 4-18. RJ21 Pinout Mapping for 10BASE-T
Punchdown Blocks
While not strictly a connector type, the punchdown block is a fairly common
component in many Ethernet 10BASE-T installations that use 25-pair cable. The
punchdowns are bayonet pins to which UTP wire strands are connected. The
bayonet pins are arranged in 50 rows of four columns each. The pins that make up
the punchdown block are identified by the row and column they are members of.
Each of the four columns is lettered A, B, C, or D, from leftmost to rightmost. The
rows are numbered from top to bottom, one to 50. Thus, the upper left hand pin is
identified as A1, while the lower right hand pin is identified as D50.
49
27
26
2
1
+ -
Transmit Transmit
Receive Receive
50
48
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46
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3
2
1
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