Service manual

Appendix B - Hardware Specifications and Cabling 97
Cyclades-TS Installation & Service Manual
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If your application is outside the above limits (high speed, long distances), you will need better quality (low-
impedance, low-capacitance) cables.
Successful RS-232 data transmission depends on many variables that are specific to each environment. The
general rules above are empirical and have a lot of safety margins built-in.
Connectors
The connector traditionally used with RS-232 is the 25-pin D-shaped connector (DB-25). Most analog modems
and most older computers and serial equipment use this connector. The RS-232 interface on DB-25 connector
always uses the same standard pin assignment.
The 9-pin D-shaped connector (DB-9) saves some space and is also used for RS-232. Most new PC COM
ports and serial equipment (specially when compact size is important) uses this connector. RS-232 interfaces
on DB-9 connectors always use the same standard pin assignment.
The telephone-type modular RJ-45 plug and jack are very compact, inexpensive and compatible with the phone
and Ethernet wiring systems present in most buildings and data centers. Most networking equipment and new
servers use RJ-45 connectors for serial communication. Unfortunately there is no standard RS-232 pin assignment
for RJ-45 connectors. Every equipment vendor has its pin assignment.
Most connectors have two versions. The ones with pins are said to be “male” and the ones with holes are said to
be “female”.