Network Wiring

Category 5 cable uses 4 twisted-pair cables, for a total of 8 individual wires. The cable supports a maximum distance of 100 meters (328 feet), although that distance may be extended if a repeater is used (in computer networking: a router or switch). The cable should not be bent more than 4 times the diameter of the cable and bundled with no more than 100 other Cat-5 cables. The maximum safe operating temperature is 45°C (113°F).

Cat-5 is common use is for Ethernet computer networks, commonly transmitting at 10mbit/s (10BASE-T / 1.25MB/sec), 100mbit/s (100BASE-TX / 12.5MB/sec), and 1000mbit/s (1000BASE-T / 125MB/sec) megabits per second. 10BASE-T and 100BASE-TX use only 2 twisted pair cables (4 wires), leaving 4 wires unused. While it would be against the written standards, these spare wires can be used for a second network connection, 2 phone lines, or Power over Ethernet if a special adapter is used. 1000BASE-T on the other hand, uses all 8 wires.

As previously mentioned, Cat-5 can be used for purposes other than computer networking including phones or even security systems including transmitting video data from security cameras in some instances. Cat-5 uses 24 gauge wire which safely carries direct current at 360mA at 50V (36W DC voltage). Anything below these limits theoretically could transmit successfully over Cat-5.

Patch Cables

T568A is the recommended format for networks by the TIA/EIA-568 standard and is required by the U.S. government for all federal government work. T568B use to be the traditional format for networks in the U.S. because it matched the legacy AT&T 258A wiring scheme.

T568A

White
Green
Green White
Orange
Blue White
Blue
Orange White
Brown
Brown
                                                       

T568B

White
Orange
Orange White
Green
Blue White
Blue
Green White
Brown
Brown
                                                       

Crossover Cables

In the rare event an Ethernet cable is needed to directly connect two computers, a special crossover cable must be used. Crossover cables have a T568A (or T568B) on one end and the other end has the twisted pairs swapped.

T568A Crossover

White
Orange
Orange White
Green
White
Brown
Brown Green Blue White
Blue
                                                       

T568B Crossover

White
Green
Green White
Orange
White
Brown
Brown Orange Blue White
Blue
                                                       

The Lazy 2 Pair Crossover Cable

Best practice is to cross all 4 twisted pairs so that the crossover cable can be used with 10BASE-T, 100BASE-TX, and 1000BASE-T. However, since 10BASE-T and 100BASE-TX only use 2 of the 4 twisted pairs, it is only necessary to cross the used ones if the cable will never be used for gigabit Ethernet.

RJ31X

A RJ31X is a specially wired RJ45 plug that allows a security system to share the telephone line with standard household phones versus paying for an additional telephone line just for the security system. In the event of an alarm if the phone is in use or off the hook, the RJ31X disconnects the house phones temporarily so the the security system can take over the phone line and make the call to the alarm company.

A standard 8P8C/RJ45 connector (same as Ethernet) plugs into the RJ31X jack to connect the security system. Usually, Cat-5 cable is used, however a 4 conductor telephone line can be used as a substitute providing it terminates with a RJ45 connector and not the typical RJ11.

Two standard telephone lines are wired to the RJ31X, one from the phone company and one to the rest of the phone system. Both transmit conductors are spliced together, as well as both receives. The individual transmit and receive conductors are then also spliced to their respective pins in the RJ31X jack.

Security System Phone1 Cat-51 RJ45 Jack Internal Wiring Phone System
Receive 1 <==             Pin 1 <==+==> House Phones
      Pin 22    |   
      Pin 32    |   
Recieve <==             Pin 4 <==+==[ Telephone Company
Transmit <==             Pin 5 <==+==[ Telephone Company
      Pin 62    |   
      Pin 72    |   
Transmit 1 <==             Pin 8 <==+==> House Phones

1: 4 conductor telephone line or Cat-5 cable can be used. Both are shown to demonstrate the proper wiring to the pins on the RJ31X

2: Pins 2, 3, 6, and 7 are unused in a RJ31X plug