Cisco EF4116 Hardware Installation And Maintenance Manual page 39

Figure 2-15
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. X.21 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 network end of the X.21 adapter cable is a standard DB-15 connector. (See Figure 2-16.)
X.21 cables are available as either DTE (DB-15 plug) or DCE (DB-15 receptacle).
Figure 2-16
EIA-530 Connections
EIA-530, 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, instead of the
37-pin connectors used for EIA/TIA-449. 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 or faster speeds over short
distances.
The EIA-530 adapter cable is available in DTE mode only. The network end of the EIA-530 adapter
cable is a standard DB-25 plug commonly used for EIA/TIA-232 connections. Figure 2-17 shows
the DB-25 connector at the network end of the adapter cable.
Figure 2-17
V.35 Adapter Cable Connectors, Network End
X.21 Adapter Cable Connectors, Network End
1
8
9
15
EIA-530 Adapter Cable Connector, Network End
DTE
DCE
DTE
DCE
DTE
Network Connection Considerations
Preparing for Installation 2-17