Network and Telecommunication Cables

Telecommunications and networking room with racks of switches and routers, telco punchdown blocks, and a Linux firewall.

First, the fundamentals: Below is an ANSI/TIA/EIA-422-B (formerly RS-422) or ITU-T V.35 serial cable for connecting a Cisco router's serial port to a T1/DS1 interface.

Cisco V.35 or ANSI/TIA/EIA-422-B (formerly RS-422) or ITU-T V.11 serial cable.

The V.35 interface is now specified as ITU-U V.11. V.35/V.11 is for data communication at speeds up to 10 Mbps.

This type of cable has a DB-60 connector at the router end, and a Winchester block connector at the network interface end. Cisco's description, including pinouts, is here.

At left is one end of a Category 5 Ethernet cable, or more formally, ANSI/TIA/EIA-568-A.

The connector is informally known as an RJ45. To be pedantic, that's incorrect: it is really an 8P8C modular connector.

Why is "RJ45" incorrect? The RJ45 standard refers to the physical connector and the wiring pattern. A true RJ45 was used for an analog telephone connection and was intended for use with a high-speed modem. Pins 5 and 4 were the tip and ring, respectively, of a single telephone line, and pins 7 and 8 were a programming resistor.

The wiring of a true 8P8C connector is:

Pin	EIA T568A		EIA T568B
Pin	Wire, of pair	Color	Wire, of pair	Color
1	1 of 3	white/green	1 of 2	white/orange
2	2 of 3	green	2 of 2	orange
3	1 of 2	white/orange	1 of 3	white/green
4	2 of 1	blue	2 of 1	blue
5	1 of 1	white/blue	1 of 1	white/blue
6	2 of 2	orange	2 of 3	green
7	1 of 4	white/brown	1 of 4	white/brown
8	2 of 4	brown	2 of 4	brown
To make a crossover cable, wire one end as T568A and the other as T568B.

Right to left in the picture above, or top to bottom in the picture below, are pins 1 through 8.

10BASE-T (Ethernet) and 100BASE-TX (Fast Ethernet) use wire pairs 2 and 3, or wires 1/2 and 3/6.

10BASE-T uses two differential voltages: +2.5V or -2.5V, signalling at 10 Mbaud.

Electrical characteristics for Cat.5e
Property	Value
Impedance at 100 MHz	100±15Ω
Capacitance at 800 Hz	52 pF/m
Inductance	525 nH/m
DC resistance	≤0.188Ω/m
Propagation speed	0.64c
Propagation delay	4.8-5.3 ns/m

100BASE-TX uses three differential voltages: +1V, 0V or -1V. 4B5B binary encoding generates a signal clocked at a 125 MHz symbol rate. Data bits are grouped into groups of 4 bits each, each data block converted to a 5-bit block guaranteed to have at least two transistions and solve problems of receiver clock synchronization, DC equalization, and spectrum shaping.

1000BASE-T (Gigabit Ethernet) uses all four wire pairs, signaling with 5-level pulse amplitude modulation at a 125 Mbaud symbol rate.

Category	Bandwidth
3	16 MHz
4	20 MHz
5, 5e	100 MHz
6	250 MHz
6a	500 MHz
7	600 MHz
7a	1000 MHz

All these standards should be able to communicate over cables up to 100 meters long. Cables are rated in terms of their RF bandwidth rather than supported bit rate, as listed in the table at right.

The wire pairs are twisted together to create a bundle of balanced transmission lines and reduce crosstalk between pairs. The twisting is at 1.5-2 cm per turn.

The wires are #24 AWG or 0.205 mm², rated for 0.577 A maximum current.

8P8C connector, pins 1 through 8 from top to bottom.

Category 5 (or cat-5) Ethernet cable plugging into Cisco switches.

At right and immediately below, Category 5 Ethernet cables plugging into a bank of Cisco switches, along with four fiber optic lines (smaller diameter yellow and orange lines).

ANSI/TIA/EIA-422-B (formerly RS-422) or ITU-T V.11 serial connections to a bank of three Cisco routers.

Above are fiber optic network connections.

At right are ANSI/TIA/EIA-422-B serial connections to three Cisco routers.

At left and below are a Fujitsu FLM 600 MD / 2400 LS OC-12 SONET ring and FLM-150 SONET interfaces.

Above at left is a Tsunami 100 5.3/5.8 GHz wireless Ethernet bridge mounted above a Cisco Catalyst 2950 switch with 24 Ethernet ports and two fiber ports,

Below is an ATM switch at left and a Cisco Catalyst 48-port Ethernet switch.