BNC Connector The BNC (Bayonet Neill-Concelman) connector is a very common type of RF connector used for terminating coaxial cable. BNC connectors were commonly used on 10base2 thinnet Ethernet networks, both on cable interconnections and Network Interface Cards (NIC). Other types of BNC connectors are T Connector, Barrel N-Type Connector and Terminator Connector.




BNC T Connector Barrel----BNC Connector----------BNC Connector------------NIC with BNC

RJ45 Connector

Twisted-pair Ethernet standards are such that the majority of cables can be wired "straight-through" (pin 1 to pin 1, pin 2 to pin 2 and so on), but others may need to be wired in the "crossover" form (receive to transmit and transmit to receive).

10BASE-T and 100BASE-TX only require two pairs to operate, located on pins 1 plus 2 and pins 3 plus 6. Since 10BASE-T and 100BASE-TX need only two pairs and Category 5 cable has four pairs, it is possible, but not standards compliant, to run two network connections (or a network connection and two phone lines) over a Category 5 cable by using the normally unused pairs (pins 4–5, 7–8) in 10- and 100-Mbit/s configurations. In practice, great care must be taken to separate these pairs as most 10/100-Mbit/s hubs, switches and PCs internally hardwire pins 4–5 together and pins 7–8 together, thereby creating a short-circuit across each "unused" pair. Moreover, 1000BASE-T requires all four pairs to operate, pins 1 and 2, 3 and 6 — as well as 4 and 5, 7 and 8.

It is conventional to wire cables for 10- or 100-Mbit/s Ethernet to either the T568A or T568B standards. Since these standards differ only in that they swap the positions of the two pairs used for transmitting and receiving (TX/RX), a cable with T568A wiring at one end and T568B wiring at the other is referred to as a crossover cable. The terms used in the explanations of the 568 standards, tip and ring, refer to older communication technologies, and equate to the positive and negative parts of the connections.

A 10BASE-T or 100BASE-T node such as a PC also called MDI that transmits on pin 1 and 2 and receives on pin 3 and 6 to a network device uses a "straight-through" cable in the MDI wiring pattern. A straight-through cable is usually used to connect a node to its network device. In order for two network devices or two nodes to communicate with each other (such as a switch to another switch or computer to computer) a crossover cable is often required at speeds of 10 or 100 Mbit/s. If available, connections can be made with a straight-through cable by means of an MDI-X port, also known as an "internal crossover" or "embedded crossover" connection. Hub and switch ports with such internal crossovers are usually labelled as such, with "uplink" or "X". For example, 3Com usually labels their ports 1X, 2X, and so on. In some cases a button is provided to allow a port to act as either a normal or an uplink port.

To connect two computers directly together without a switch, an Ethernet crossover cable is often used. Although many modern Ethernet host adapters can automatically detect another computer connected with a straight-through cable and then automatically introduce the required crossover, if needed; if neither of the computers have this capability, then a crossover cable is required. If both devices being connected support 1000BASE-T according to the standards, they will connect regardless of the cable being used or how it is wired.

To connect two hubs or switches directly together, a crossover cable can be used, but some hubs and switches have an uplink port used to connect network devices together, or have a way to manually select MDI or MDI-X on a single port so that a straight-through cable can connect that port to another switch or hub. Most newer switches have automatic crossover ("auto MDI-X" or "auto-uplink") on all ports, eliminating the uplink port and the MDI/MDI-X switch, and allowing all connections to be made with straight-through cables.

A 10BASE-T transmitter sends two differential voltages, +2.5 V or −2.5 V.

100BASE-TX follows the same wiring patterns as 10BASE-T but is more sensitive to wire quality and length, due to the higher bit rates.

A 100BASE-TX transmitter sends three differential voltages, +1 V, 0 V, or −1 V.

1000BASE-T uses all four pairs bi-directionally and the standard includes auto MDI-X; however, implementation is optional. With the way that 1000BASE-T implements signaling, how the cable is wired is immaterial in actual usage. The standard on copper twisted pair is IEEE 802.3ab for Cat 5e UTP, or 4D-PAM5; four dimensions using PAM (pulse amplitude modulation) with five voltages, −2 V, −1 V, 0 V, +1 V, and +2 V While +2 V to −2 V voltage may appear at the pins of the line driver, the voltage on the cable is nominally +1 V, +0.5 V, 0 V, −0.5 V and −1 V.

Unlike earlier Ethernet standards using broadband and coaxial cable, such as 10BASE5 (thicknet) and 10BASE2 (thinnet), 10BASE-T does not specify the exact type of wiring to be used but instead specifies certain characteristics that a cable must meet. This was done in anticipation of using 10BASE-T in existing twisted-pair wiring systems that may not conform to any specified wiring standard. Some of the specified characteristics are attenuation, characteristic impedance, timing jitter, propagation delay, and several types of noise. Cable testers are widely available to check these parameters to determine if a cable can be used with 10BASE-T. These characteristics are expected to be met by 100 meters of 24-gauge unshielded twisted-pair cable, and 100 meters is the stated maximum length for baseband signal runs. However, with high quality cabling, cable runs of 150 meters or longer are often obtained and are considered viable by most technicians familiar with the 10BASE-T specification, though – as with all CSMA/CD network environments – the absolute limit on run length is determined by the size of the collision domain and cable quality. In reality, what meets the standards may not work, and those that do not meet the standards might work. 100BASE-TX and 1000BASE-T were both designed to require a minimum of Category 5 cable and also specify a maximum cable length of 100 meters, though in practice category 5e or above is generally recommended for 1000BASE-T. Furthermore while 10BASE-T is more tolerant of poor wiring such as split pairs, poor terminations and even use of short sections of flat cable, 100BASE-T is less tolerant, and 1000BASE-T is even less so. Since cable testing is often limited to checking if a connection works with Ethernet, running faster speeds over existing cable is often problematic. This problem is made worse by the fact that Ethernet's auto-negotiation takes account only of the capabilities of the end equipment, not of the cable in between.
RJ45 Socket (Keystone jack)