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Serial Cable Length Limits (RS232, V.35, RS530, RS422/449)
Parallel Cable Length Limits
Serial Cable Length Limits (RS-232, V.35, RS-530, RS-422/449)
Table below lists the maximum permissible cable lengths for various protocols at various representative data rates. These lengths are as
specified in the EIA RS232C, CCITT V.55 and RS422 interface standards.
Material requirements:
* Conductor size and type: 24 AWG, twisted pair.
* Nominal capacitance: 15.5 picofarads per foot (between
conductors of each pair);
27.5 picofarads per foot (from each conductor to shield).
* Nominal DC resistance (each conductor): 24.0 ohms per 1000 feet.
* Nominal DC resistance (shield): 2.35 ohms per 1000 feet.
* Shield type: Overall braided with drain wire.
* Approval: Underwriters Laboratories (UL).
DTE Data Rate [kb/s] |
Maximum DTE Cable Lengths [ft] |
RS232C |
V.35 |
RS449/422 |
RS530/422 |
56 or 64 |
10 |
4000 |
4000 |
4000 |
224 or 256 |
N/A |
3500 |
1700 |
1700 |
896 or 1024 |
N/A |
1700 |
350 |
350 |
N/A - not aplicable (these rates cannot be used for RS232C interface |
NOTE on RS-232 Serial Cables
At lower peripheral speeds of up to 9600 baud,serial interfaces can usually operate
over cables up to 50 feet long. Use of special high quality cable may in some cases allow this limit to be extended to as much as 150 feet.
Parallel Cables Length Limits
Older style Centronics parallel cables, can rarely be more than 15 feet long and still operate correctly, and 9 to 12 feet is a safer limit. The IEEE-1284 can go up to 30feet in length. |
