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X.21 Connections
The X.21 interface uses a 15-pin connection for balanced circuits and is commonly used in the
United Kingdom to connect public data networks. The X.21 interface relocates some of the logic
functions to the DTE and DCE interfaces and, as a result, requires fewer circuits and a smaller
connector than EIA/TIA-232.
The router (FSIP) end of all X.21 adapter cables is a high-density 60-pin plug. The opposite
(network) end of the adapter cable is a standard DB-15 connector.
Figure 17 shows the connectors at the network end of the X.21 adapter cable.
Figure 17
EIA-530 Connections
The EIA-530 interface, which supports balanced transmission, provides the increased functionality,
speed, and distance of EIA/TIA-449 on the smaller, DB-25 connector used for EIA/TIA-232. The
EIA-530 interface is used primarily in the United States. The EIA-530 standard was created to
support the more sophisticated circuitry of EIA/TIA-449 on the large number of existing
EIA/TIA-232 (DB-25) hardware. Like EIA/TIA-449, EIA-530 refers to the electrical specifications
of EIA/TIA-422 and EIA/TIA-423. Although the specification recommends a maximum speed of
2 Mbps, EIA-530 is used successfully at 4 Mbps and at even faster speeds over short distances.
The router (FSIP) end of the EIA-530 adapter cable is a high-density 60-pin plug. The opposite
(network) end of the adapter cable is a standard DB-25 plug commonly used for EIA/TIA-232
connections.
Figure 18 shows the DB-25 connector at the network end of the adapter cable.
Figure 18
X.21 Adapter Cable Connectors, Network End
8
1
9
15
EIA-530 Adapter Cable Connector, Network End (Available in DTE Only)
FSIP Port Adapters, Interface Cables, and Connections
DTE
DCE
DTE
Fast Serial Interface Processor (FSIP) Installation and Configuration
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