(i) The RJ-21 connector has 50 pins with 25 pins at one end and 25 pins at the other end.
(ii) It is also called as champ connector or Amphenol Connector.
(iii) Amphenol Connector is a connector manufacturer.

(i) Ethernet port is an opening which is a part of an Ethernet card.
(ii) It accepts RJ45 connector with Ethernet cable.
(iii) It is found on personal computers, laps routers, switches, hubs and modems.

1. Twisted Pair Cables is type of cable with two or more insulated wires twisted together.
2. Its speed starts from 10 mbps to 100 mbps.

There are two types of fibre optic cables available.
One is single-mode and another is Multimode.
(i) Single-mode cables are used for long distance transmission and at a high cost.
(ii) Multimode cables are used for short distance transmission at a very low cost.

(i) A cable interconnecting two devices directly is known as a null modem cable.
(ii) The crossover Ethernet cable is an example of the null modem cables.

(i) The RJ45 connector looks similar like a telephone jack but it looks a slightly wider. 
(ii) In RJ45 the "RJ" stands for the Registered Jack and the "45" simply refers to the interface standard.
(iii)The RJ45 connector is a small plastic cube. It has eight pins.
(iv) It is connected to each end of the Ethernet cable. It is also known as 8P8C connector.
(v) These plugs (connector) are inserted into Ethernet port of the network card.

There are 3 types of wiring techniques to construct the Ethernet cable. It is also known as color coding techniques. They are:
(a) Straight-Through wiring:
(b) Cross-Over wiring; and
(c) Roll-Over wiring.
(a) Straight-Through Wiring:
1. Ethernet cables used for Ethernet connections are "straight-through cables" and these cable wires are in the same sequence at both ends sof the cable.
2. The straight-through wiring cables are mostly used for connecting PC/NIC card to a hub.
3. This is a simple physical connection used in printers, computers and other network interfaces.


(b) Cross-Over Wiring:
1. We need a cross-over cable when ever we connect two computers (or) Ethernet devices directly together without a hub, we use crossover cable.
2. Then the pairs (Tx and Rx lines) will be crossed which means pin 1 & 2 of the plug on one end are connected with pin 3 & 6 of the plug on other end and vice-versa.
3. The easiest way to make a cross-over cable is to make one end to T568A colour coding and the other end to T568B.



(c) Roll-Over Wiring:
1. Roll-over cable is a type of null-modem cable that is often used to connect a device console port to make programming changes to the device.
2. This wire has opposite pin arrangements, all the cables are rolled over to different arrangements.
3. In this cable, the coloured wires are reversed on other end. (i.e.,) The pins in one end are connected with other end in reverse order. (i.e.) (Pin 1 to 8, 2 to 7, 3 to 6, 4 to 5, 5 to 4, 6 to 3, 7 to 2, 8 to 1)
4. It is also known as Yost cable (or) console cable. It is typically flat to distinguish it from other types of network cabling.
5. These all 3 arrangements are used to perform an interface change. But all these 3 arrangements transmits the data at same speed only.

Registered Jacks: A Registered Jack commonly known as RJ is a network interface used for network cabling, wiring and jack construction. The primary function of the registered jack is to connect different data equipment and telecommunication devices. The commonly known registered jacks are RJ-11, RJ-45, RJ-21,and RJ-28. The registered jack refers to the male physical connector (Plug), a female physical connector (Jack) and it's wiring.
Types of Registered Jacks:
(i) RJ-11 :
It is the most popular modern form of registered jack. It is found in home and used for landline phones. There are 6 pins where the two pins give the transmission configuration, the two pins give the receiver configuration and the other two pins will be kept for reserved.
(ii) RJ-14 and RJ-61:
The RJ-14 is also used in telephone lines like RJ-11. It has 6 pins whereas the RJ-61 has 8 pins. RJ-61 uses the twisted pair cable to connect the network devices.
(iii) RJ-21:
The RJ-21 connector has 50 pins with 25 pins at one end and 25 pins at the other end. It is also called as champ connector or Amphenol connector. The Amphenol is a connector manufacturer.The RJ-21 interface is typically used for data-communication trucking applications.