Cables Explained
Type Description Speed
Category 5 UTP Unshield twisted pair (UTP) high performance. The twisting gives the cable a certain immunity from the infiltration of unwanted interface. The most common used in the USA. 10 or 100Mbps
Category 5 SCTP Screened twisted pair (SCTP). Same as Cat5 with an additional protection from unwanted interference by an overall shield. If used, all components of the network most use SCTP. Used almost exclusively in European countries. 10 or 100Mbps
Category 5E Same as CAT5 with more stringent standards and will support gigabyte Ethernet. 10/100Mbps or 1000Gbps
Category 6 Same as CAT5E with even more stringent standards and will support gigabyte Ethernet. 10/100Mbps or 1000Gbps
Category 7 Same as CAT6 with even more stringent standards. The standard for CAT7 is still in progress. All 4 pairs are individually shielded and an overall shield enwraps all 4 pairs. It will require an entirely new connector other than RJ45 10/100Mbps or 1000Gbps
Terms Description
Crosstalk The bleeding of signals carried by one pair onto another pair through the electrical process of induction. This is an unwanted effect that can cause slow transfer or completely inhibit the transfer of data. The purpose of the wire twists is to significantly reduce crosstalk.
Ambient Noise or Electromagnetic Interference (EMI) Similar to crosstalk in that it is an unwanted signal that is induced into the cable. The difference is the ambient noise (EMI) is typically induced from a source that is external to the cable such as an electrical cable, other device or even an adjacent CAT cable.
Attenuation The loss of signal in a cable segment due to the resistance of the wire plus other electrical factors that cause additional resistance (Impedance and Capacitance for example). A longer cable length, poor connections, bad insulation, a high level of crosstalk or ambient noise will increase the total level of attenuation.
Installation Guidelines
Run all cables in a "star" configuration. they should emanate from central location. Visualize a wagon wheel with the spokes being the cable and the hub being the central location.
Cable length should not exceed 295 feet for each run.
Maintain the twists of the pairs all the way to the point of termination with no more than 0.5" untwisted.
Make gradual bends when necessary. No shaper than a 1" radius.
When using cable ties, only use moderate pressure when pulling the tie.
Cross-connect cables using the correct CAT rated punch blocks and components.
Don't ever splice cables.
Use low to moderate force when pulling cables.
Use cable lubricant when pulling cables to eliminate using a large force.
Keep cables as far away as possible from potential sources of EMI (electrical cables, transformers, light fixtures, etc.)
Install proper cable supports, no more than 5 feet apart. Cable supported by ceiling tiles usually violates most building codes.
Label every termination point. Use a unique number for each cable.
Always test every installed segment with a cable tester.
Install jacks in such a way as to avoid collecting dust.
Always leave extra slack on the cables, neatly coiled up in the ceiling or nearest concealed place.
Use grommets when passing through metal studs
Never use staples
Use plenum rated cable where building codes require it.

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Ethernet RJ-45

RJ-45 (10/100BaseT) uses pins 1,2,3 and 6,7,8 - These must be used in pairs as follows...

Pin Color
1 white/orange
2 orange
3 white/green
4 blue (not used)
5 white/blue (not used)
6 green
7 white/brown
8 brown
Pin Color
1 white/orange
2 orange
3 white/green
4 blue (not used)
5 white/blue (not used)
6 green
7 white/brown
8 brown
blue (not used)
white/blue (not used)

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Serial RS-232 with RJ-45 Jack

The following represents the most common configuration for a RS-232/RJ45 connector used on a 'dumb terminal' with a cat5 cable connected to a concentrator. If a serial port on the PC is being used, pins 2 and 3 have to be reversed. Most of the time it is only necessary to use pins 2, 3, 7 and 20.

Pin Color Signal Mnemonic
1 Black Chassis Ground GND
2 Green Transmit TXD
3 Red Receive RXD
4 Brown Requestto Send RTS
5 Orange Clear to Send CTS
6 Data Set Ready DSR
7 Yellow Signal Ground SGND
8 White Data Carrier Detect DCD
20 Blue Data Terminal Ready DTR

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