Tollfree Networks

Tollfree Networks Limited is a UK based "Independent Secondary Market Vendor" for data communications and telecom equipments.

We specialize in the sale of Secondary Sourced New Surplus, recently discontinued and refurbished Data & Telecommunication equipment as well as distribute authorized 3rd party options for local and wide area networks such as Memory, Cables and GBIC’s etc. Secondary Sourced parts are parts that are not "factory sealed new".

Tollfree Networks’ business strategy is based on the belief that the customer requires quality comprehensive technical and professional services, technical support, and product fulfilment.

As a supplier of Secondary Sourced New Surplus and Refurbished (decommissioned) Central Office networking equipment, we provide quality-networking equipments from the global market place. Our core focus is on saving our valuable customers time and money in re-sourcing the correct equipment at the right price and within the acceptable delivery time scales.

75% of our business is derived from CISCO equipment both Secondary Sourced New Surplus and Refurbished equipments. Balance 25% is derived from other leading brands such as Juniper, Extreme, Foundry, Nortel, 3COM and F5. Having excellent local and international relationships with our key suppliers, we can help your organisation achieve your objectives globally.

We have a wide spread customer base globally, each with different needs and requirements. Internet service provider rapidly building their network, to the established telecom network operators seeking to increase network efficiencies and capacity or implement next generation technology, we are well positioned to be a one-stop resource to accommodate the needs of any customer.

Fiber testing metre

The economical solution to help you save on today's costly testing operations this power meter tests both single mode and multi mode fibers quickly and accurately. And is very easy to use turn it on, select a wavelength and start testing. Hand held Power Meter measurements at 1310nm & 1550nm.

Technical Specification :
• Fiber certification with high accuracy and high resolution for both multi mode and single mode applications width 1310 nm or 1530 nm.
• Internal memory stores up to 1000 measurements and physical fiber characteristics for up to four sites.
• User friendly interface with alpha numeric membrane keypad for easy entry of testing documentation including site name, date, fiber type and length, connectors and splices.
• Lightweight and compact.
• Use the RS-232 interface and Windows® compatible OWL Reporter software to download data and print professional certificatio

Repeater

A network device used to regenerate or replicate a signal. Repeaters are used in transmission systems to regenerate analog or digital signals distorted by transmission loss. Analog repeaters frequently can only amplify the signal while digital repeaters can reconstruct a signal to near its original quality.

In a data network, a repeater can relay messages between subnetworks that use different protocols or cable types. Hubs can operate as repeaters by relaying messages to all connected computers. A repeater cannot do the intelligent routing performed by bridges and routers.

Network repeaters regenerate incoming electrical, wireless or optical signals. With physical media like Ethernet or Wi-Fi, data transmissions can only span a limited distance before the quality of the signal degrades. Repeaters attempt to preserve signal integrity and extend the distance over which data can safely travel.

Actual network devices that serve as repeaters usually have some other name. Active hubs, for example, are repeaters. Active hubs are sometimes also called "multiport repeaters," but more commonly they are just "hubs." Other types of "passive hubs" are not repeaters. In Wi-Fi, access points function as repeaters only when operating in so-called "repeater mode."

Higher-level devices in the OSI model like and routers generally do not incorporate the functions of a repeater.

In telecommunication networks, a repeater is a device that receives a signal on an electromagnetic or optical transmission medium, amplifies the signal, and then retransmits it along the next leg of the medium. repeaters overcome the attenuation caused by free-space electromagnetic-field divergence or cable loss. A series of repeaters make possible the extension of a signal over a distance. In addition to strengthening the signal, repeaters also remove the noise or unwanted aspects of the signal.

ROUTER

A router is a device that forwards data packets along networks. A router is connected to at least two networks, commonly two LANs or WANs or a LAN and its ISP's network. Routers are located at gateways, the places where two or more networks connect, and are the critical device that keeps data flowing between networks and keeps the networks connected to the Internet. When data is sent between locations on one network or from one network to a second network the data is always seen and directed to the correct location by the router. They accomplish his by using headers and forwarding tables to determine the best path for forwarding the data packets, and they use protocols such as ICMP to communicate with each other and configure the best route between any two hosts.

The Internet itself is a global network connecting millions of computers and smaller networks — so you can see how crucial the role of a router is to our way of communicating and computing.

Why Would I Need a Router?
For most home users, they may want to set-up a LAN (local Area Network) or WLAN (wireless LAN) and connect all computers to the Internet without having to pay a full broadband subscription service to their ISP for each computer on the network. In many instances, an ISP will allow you to use a router and connect multiple computers to a single Internet connection and pay a nominal fee for each additional computer sharing the connection. This is when home users will want to look at smaller routers, often called broadband routers that enable two or more computers to share an Internet connection. Within a business or organization, you may need to connect multiple computers to the Internet, but also want to connect multiple private networks — and these are the types of functions a router is designed for.

Routers for Home & Small Business
Not all routers are created equal since their job will differ slightly from network to network. Additionally, you may look at a piece of hardware and not even realize it is a router. What defines a router is not its shape, color, size or manufacturer, but its job function of routing data packets between computers. A cable modem which routes data between your PC and your ISP can be considered a router. In its most basic form, a router could simply be one of two computers running the Windows 98 (or higher) operating system connected together using ICS (Internet Connection Sharing). In this scenario, the computer that is connected to the Internet is acting as the router for the second computer to obtain its Internet connection.

Going a step up from ICS, we have a category of hardware routers that are used to perform the same basic task as ICS, albeit with more features and functions. Often called broadband or Internet connection sharing routers, these routers allow you to share one Internet connection between multiple computers.

This image shows the flow of data to multiple computers sharing one high speed Internet connection.

Broadband or ICS routers will look a bit different depending on the manufacturer or brand, but wired routers are generally a small box-shaped hardware device with ports on the front or back into which you plug each computer, along with a port to plug in your broadband modem. These connection ports allow the router to do its job of routing the data packets between each of the the computers and the data going to and from the Internet.

Depending on the type of modem and Internet connection you have, you could also choose a router with phone or fax machine ports. A wired Ethernet broadband router will typically have a built-in Ethernet switch to allow for expansion. These routers also support NAT (network address translation), which allows all of your computers to share a single IP address on the Internet. Internet connection sharing routers will also provide users with much needed features such as an SPI firewall or serve as a a DHCP Server.

Wireless broadband routers look much the same as a wired router, with the obvious exception of the antenna on top, and the lack of cable running from the PCs to the router when it is all set up. Creating a wireless network adds a bit more security concerns as opposed to wired networks, but wireless broadband routers do have extra levels of embedded security. Along with the features found in wired routers, wireless routers also provide features relevant to wireless security such as Wi-Fi Protected Access (WPA) and wireless MAC address filtering. Additionally, most wireless routers can be configured for "invisible mode" so that your wireless network cannot be scanned by outside wireless clients. Wireless routers will often include ports for Ethernet connections as well. For those unfamiliar with WiFi and how it works, it is important to note that choosing a wireless router may mean you need to beef up your Wi-Fi knowledge-base. After a wireless network is established, you may possibly need to spend more time on monitoring and security than one would with a wired LAN.

Wired and wireless routers and the resulting network can claim pros and cons over each other, but they are somewhat equal overall in terms of function and performance. Both wired and wireless routers have high reliability and reasonably good security (without adding additional products). However —and this bears repeating — as we mentioned you may need to invest time in learning more about wireless security. Generally, going wired will be cheaper overall, but setting up the router and cabling in the computers is a bit more difficult than setting up the wireless network. Of course, mobility on a wired system is very limited while wireless offers outstanding mobility features.

A router is a device in computer networking that forwards data packets to their destinations, based on their addresses. The work a router does it called routing, which is somewhat like switching, but a router is different from a switch. The latter is simply a device to connect machines to form a LAN.

How a Router Works

When data packets are transmitted over a network (say the Internet), they move through many routers (because they pass through many networks) in their journey from the source machine to the destination machine. Routers work with IP packets, meaning that it works at the level of the IP protocol.

Each router keeps information about its neighbors (other routers in the same or other networks). This information includes the IP address and the cost, which is in terms of time, delay and other network considerations. This information is kept in a routing table, found in all routers.

When a packet of data arrives at a router, its header information is scrutinized by the router. Based on the destination and source IP addresses of the packet, the router decides which neighbor it will forward it to. It chooses the route with the least cost, and forwards the packet to the first router on that route.

Types of ROUTERS

Twisted pair cable

Twisted pair cabling is a form of wiring in which two conductors are wound together for the purposes of canceling out electromagnetic interference (EMI) from external sources, electromagnetic radiation from the UTP cable, and crosstalk between neighboring pairs.

Twisting wires decreases interference because the loop area between the wires (which determines the magnetic coupling into the signal) is reduced. In balanced pair operation, the two wires typically carry equal and opposite signals (differential mode) which are combined by subtraction at the destination. The common-mode noise from the two wires (mostly) cancel each other in this subtraction because the two wires have similar amounts of EMI that are in phase. Differential mode also reduces electromagnetic radiation from the cable, along with the attenuation that it causes.

The twist rate (also called pitch of the twist, usually defined in twists per metre) makes up part of the specification for a given type of cable. Where pairs are not twisted, one member of the pair may be closer to the source than the other, and thus exposed to slightly different induced EMF.

Where twist rates are equal, the same conductors of different pairs may repeatedly lie next to each other, partially undoing the benefits of differential mode. For this reason it is commonly specified that, at least for cables containing small numbers of pairs, the twist rates must differ.

In contrast to FTP (foiled twisted pair) and STP (shielded twisted pair) cabling, UTP (unshielded twisted pair) cable is not surrounded by any shielding. It is the primary wire type for telephone usage and is very common for computer networking, especially as patch cables or temporary network connections due to the high flexibility of the cables.

Unshielded twisted pair (UTP)

Unshielded twisted pair cable.

Twisted pair cables were first used in telephone systems by Bell in 1881 and by 1900 the entire American network was twisted pair, or else open wire with similar arrangements to guard against interference. Most of the billions of conductor feet (millions of kilometres) of twisted pairs in the world are outdoors, owned by telephone companies, used for voice service, and only handled or even seen by telephone workers. The majority of data or Internet connections use those wires.

UTP cables are not shielded. This lack of shielding results in a high degree of flexibility as well as rugged durability. UTP cables are found in many ethernet networks and telephone systems. For indoor telephone applications, UTP is often grouped into sets of 25 pairs according to a standard 25-pair color code originally developed by AT&T. A typical subset of these AD1L colors (white/blue, blue/white, white/orange, orange/white) shows up in most UTP cables.

For urban outdoor telephone cables containing hundreds or thousands of pairs, different twist rates for each pair are impractical. For this design, the cable is divided into smaller but identical bundles, with each bundle consisting of twisted pairs that have different twist rates. The bundles are in turn twisted together to make up the cable. Because they reside in different bundles, twisted pairs having the same twist rate are shielded by physical separation. Still, pairs having the same twist rate within the cable will have greater crosstalk than pairs of different twist rate. Thus to minimize crosstalk within a large cable, careful pair selection is important. Twisted pair cabling is often used in data networks for short and medium length connections because of its relatively lower costs compared to fiber and coaxial cabling.

Uses

Unshielded twisted pair (UTP) cabling, because of its 100-year history of use by telephone systems, both indoors and out, is also the most common cable used in computer networking. It is a variant of twisted pair cabling. UTP cables are often called ethernet cables after Ethernet, the most common data networking standard that utilizes UTP cables.

Historical note

Wire transposition on top of pole.

Soon after the invention of the telephone, open wire lines were used for transmission. Two wires, strung on either side of cross bars on poles, share the route with electrical power lines. At first, interference from power lines limited the practical distance for telephone signals. Discovering the cause, engineers devised a method, called wire transposition, to cancel out the interference, where once every several poles, the wires crossed over each other. In this way, the two wires would receive similar EMI from power lines. Today, such open wire lines with periodic transpositions can still be found in rural areas. This represented an early implementation of twisting with a twist rate of about 4 twists per kilometre.

Cable shielding

Main article: Electromagnetic shielding

S/STP, also known as S/FTP.

Twisted pair cables are often shielded in attempt to prevent electromagnetic interference. Because the shielding is made of metal, it may also serve as a ground. However, usually a shielded or a screened twisted pair cable has a special grounding wire added called a drain wire. This shielding can be applied to individual pairs, or to the collection of pairs. When shielding is applied to the collection of pairs, this is referred to as screening. The shielding must be grounded for the shielding to work.

Foiled Twisted Pair cable.

Shielded twisted pair (STP)

STP cabling includes metal shielding over each individual pair of copper wires. This type of shielding protects cable from external EMI (electromagnetic interferences). e.g. the 150 ohm shielded twisted pair cables defined by the IBM Cabling System specifications and used with token ring networks.

Screened shielded twisted pair (S/STP)

S/STP cabling, also known as Screened Fully shielded Twisted Pair (S/FTP), is both individually shielded (like STP cabling) and also has an outer metal shielding covering the entire group of shielded copper pairs (like S/UTP). This type of cabling offers the best protection from interference from external sources.

Screened unshielded twisted pair (S/UTP)

S/UTP, also known as Fully shielded (or Foiled) Twisted Pair (FTP), is a screened UTP cable.

Advantages

• It is a thin, flexible cable that is easy to string between walls.
• Because UTP is small, it does not quickly fill up wiring ducts.
• UTP costs less per foot than any other type of LAN cable.

Disadvantages

• Twisted pair’s susceptibility to the electromagnetic interference greatly depends on the pair twisting schemes (usually patented by the manufacturers) staying intact during the installation. As a result, twisted pair cables usually have stringent requirements for maximum pulling tension as well as minimum bend radius. This relative fragility of twisted pair cables makes the installation practices an important part of ensuring the cable’s performance.

Minor twisted pair variants

• Nonloaded twisted pair: A twisted pair that has no intentionally added inductance. Wires that go more than a mile (1.6 km) usually have load coils to increase their inductance, unless they are to carry higher than voiceband frequencies.

See also

• Balanced line
• Tip and ring
• Ethernet over twisted pair
• Registered jack
• TIA/EIA-568-B
• CAT 5

RJ45, RJ11 & RJ12 connector

RJ11, RJ12, and RJ45 Pinning and Wiring Schemes

The terms RJ11, RJ12, RJ45, keyed RJ45 and such are frequently used incorrectly to describe modular jacks and plugs, however, to be precise, modular plugs and jacks should be referred to as described below:

	4 Position Modular Jack (Often called an RJ11 jack or plug.)
	6 Position Modular Jack (Often called an RJ11 or RJ12 jack or plug.)
	6 Position Modified Modular Jack (Often called an MMJ jack or plug.)
	8 Position Modular Jack (Often called an RJ45 jack or plug.)
	8 Position Keyed Modular Jack (Often called an RJ45 keyed jack or plug.)

Common Wiring Configurations:

	USOC RJ11 or RJ11C - One pair of wires (pair 1) in a 4, 6, or 8 position modular jack. Yes, the 4 position modular plug will plug into the 6 position and 8 position modular jack, and the 6 position modular plug will plug into the 8 position modular jack.
	USOC RJ14 or RJ14C - Two pairs of wires in a 4, 6, or 8 position modular jack. Pair 1 would be the two center pins, pair 2 on the next two pins outward. Yes, the 4 position modular plug will plug into the 6 position and 8 position modular jack, and the 6 position modular plug will plug into the 8 position modular jack.
	USOC RJ25 or RJ25C - Three pairs of wires in a 6 or 8 position modular jack. Pair 1 would be the two center pins, pair 2 on the next two pins outward, pair 3 on the next two pins outward. Yes, the 6 position modular plug will plug into the 8 position modular jack. Although Ethernet networking cannot be run through this pin configuration, UTP (Unshielded Twisted Pair cable) Token Ring can be run on the two middle pairs of wires.
	USOC RJ48 or RJ48C - Four pairs of wires in an 8 position modular jack. Pair 1 would be the two center pins, pair 2 on the next two pins outward, pair 3 on the next two pins outward, and pair 4 on the outermost pins. Although ethernet networking cannot be run through this pin configuration, UTP token ring can be run on the two middle pairs of wires (pins 4 and 5, and pins 3 and 6 in the image).
	568A Wiring Scheme - Often used in Ethernet (10BaseT) on pairs 3 and 2. To use in Fast Ethernet (100BaseT), category 5 jacks, plugs, patch panels, and cables must be used. This configuration can also be used in Token Ring networking on pairs 1 and 2. Pin 1 = T3 Pin 2 = R3 Pin 3 = T2 Pin 4 = R1 Pin 5 = T1 Pin 6 = R2 Pin 7 = T4 Pin 8 = R4
	568B Wiring Scheme (Same as the AT&T 258A Wiring Scheme) - Often used in Ethernet (10BaseT) on pairs 2 and 3. To use in Fast Ethernet (100BaseT), category 5 jacks, plugs, patch panels, and cables must be used. This configuration can also be used in Token Ring networking on pairs 1 and 3. Pin 1 = T2 Pin 2 = R2 Pin 3 = T3 Pin 4 = R1 Pin 5 = T1 Pin 6 = R3 Pin 7 = T4 Pin 8 = R4
	Modified Modular Jack (MMJ) Wiring Scheme by Digital Equipment Corporation (DEC®) uses a completely proprietary wiring scheme. Pin 1 = DTR Pin 2 = TXD+ Pin 3 = TXD- Pin 4 = RXD- Pin 5 = RXD+ Pin 6 = DSR

Crimping tools

CRIMPING TOOL :

Crimping tool is network equipment. Its very useful for us. This is easily available in market. its use is to crimp the RJ11 and Rj45. This crimping is also use to cut the wires or cables. to prevent the electric shock in this equipment have a rubber grip. This Crimping tool is doing work more quickly & very much clearly. This crimping tool advantage is, it is easily available in market. & it is not much expensive. this is available in different shape & different quality.