Serial Cable Length Limits (RS232, V.35, RS530, RS422/449) SCSI Cable Length Limits 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.
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