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Trend Observer
PC based distributed analyser with decode, reporting, RMON2, SNMP, and Ethernet switch control

Technology Information

Some of the more well known forms of xDSL are listed below:

IDSL ISDN Digital Subscriber Line
HDSL High Bit-Rate Digital Subscriber Line
SDSL Symmetric Digital Subscriber Line
ADSL Asymmetric Digital Subscriber Line
VDSL Very High Bit-Rate Digital Subscriber Line
RADSL Rate Adaptive Asymmetric Digital Subscriber Line

All too often not considered within the scope of xDSL simply because ISDN is the commonly used terminology and has been internationally in use for many years. The two bearer channels of ISDN each deliver 64Kbp/s and may be bonded by a user application to provide a single delivery of 128Kbp/s. Again it is an application which “unpacks” the data. One advantage of ISDN is that the signalling protocol is entirely separate from the bearer channels and so “housekeeping” is an independent operation, hence basic rate is often referred to as 2B+D.

HDSL provides an improved method of transmitting T1 (1.55 Mbps) or E1 (2.048 Mbps) over twisted-pair copper lines. HDSL transmits 1.544 Mbps or 2.048 Mbps using bandwidths ranging from 80 kHz to 240 kHz instead of the 1.5 MHz used by AMI, the traditional method of transmitting T1/E1. Thislower frequency generates less corrup-tionof the cable spectrum enablingmore than one circuit in a multi-pairbundle. HDSL transmission uses typically 2 pairs for T1 and up to three pairs for E1. This may be seen as adisadvantage, however, it is highlylikely that these pairs will already be inplace and therefore will not require thecostly provision of new cables. A sec-ond version of HDSL, known somewhat unsurprisingly as HDSL II, can offer the ame performance as HDSL, but using a single twisted-pair. Deployment of HDSL II has a great deal of appeal to the large national carriers as it gives them all the benefits of using their installed base of copper pairs for high bandwidth applications yet minimises the number of pairs used. This tech-nique is now being deployed or tested in a number of countries.

SDSL is in essence a version of HDSL that can transmit T1 or E1 signals utilising a single twisted-pair, and typi-cally operating over POTS, giving the benefit of supporting POTS and T1/E1 simultaneously. There is, however, a distance limitation of around 10,000 feet. At face value SDSL would appear ideal for delivering high-speed access to individual subscriber premises for applications such as remote LAN or Internet access. Consideration, howev-er, should be given to the fact that ADSL can achieve higher data rates at the 10,000 feet limitation of SDSL andthat the typically usage of remote LAN and Internet access is by nature asymmetric.

ADSL Asymmetric Digital Subscriber Line
ADSL is one of the hottest topics around at the moment and it is easy to understand why. Depending on the form of ADSL deployed it is possible to achieve downstream (towards the user) speeds up to 8 Mbps and upstream (towards the service provider) speeds up to 1.5 Mbps. This asymmetric nature of ADSL makes it very attractive for applications that typically download much more data than is sent. The most obvious of these is Internet usage, however, video on demand is potentially the most exciting.
A variety of ADSL formats are being proposed at this time and they are all based on a trade-off between cost, complexity and performance. In vogue at the moment is G.Lite ADSL with downstream speed of 1.5Mbps and upstream of 384Kbps. This could well be the most user-friendly form of DSL and could become the implementation of choice for domestic users. The cost of equipment and service will almost certainly be lower than the other varieties of DSL.

VDSL is the highest speed DSL technology with data rates up to 52 Mbps downstream and up to 2.3 Mbps upstream. To achieve this speed the maximum distance from the exchange to the user is between 1,000 and 4,500 feet. VDSL is still very much at an experimental stage and no real world applications are in use.

RADSL Rate Adaptive Asymmetric Digital Subscriber Line
RADSL operates at the same band-widths as ADSL with the added ability of adjusting bandwidth to suit the quality of the line during the actual transmission.

Testing DSL technology

The advantages of xDSL technologies are self-evident, but what must we consider to be the potential problems?
In most cases we are dealing with a legacy infrastructure and topology which, because of bridge taps, mis-matching and the general degradation of the electrical characteristics of the line, may not be capable of supporting DSL services efficiently. The first step is to establish that the line is capable of supporting the chosen DSL technology and secondly, once operational, to be able to determine the fault should problems occur.
The procedures for this fall into two categories, analogue testing to determine the quality and appropriateness of the line and digital testing to determine the quality and correctness of the service. Quite simply, problems associated with quality of service can be caused by configuration issues or by the physical characteristics of the line, the latter requiring further analogue tests to determine the problem. The physical characteristics which determine DSL suitability include line length, cable suitability, bandwidth availability, environmental noise, thermal/mechanical effects, cross talk, impedance, terminations, bridge taps, insulation, and split pairs. Digital testing requires a tester with the capability to simulate a DSL modem or to replace the DSL modem, known in Trend as “Golden Modem” operation.

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Let’s get some of the terminology clear

What is attenuation?

Attenuation is signal loss due to the diminishing availability of signal energy, or signal power. As a analog or digital signal traverses across a medium, it fades. High attenuation may lead to the inability to recover the signal on the far end. Signal repeaters may be used on the transmission path to periodically boost the signal strength. Baseband transmission is extremely limited to attenuation. Broadband much less so. In addition, wireless communications is much less susceptible to attentuation that is wireline communications such as xDSL or cable modems.

What is crosstalk?

Crosstalk refers to the interference between channels. In the xDSL world, the interference between nearby cables can have a negative impact on the performance of the affected cable(s). Have you ever been on the phone and heard some other conversation, not yours, in the background? If so, you have experienced the effect of crosstalk.

Near-end crosstalk (NEXT) occurs when the transmitter sends a signal and a nearby transceiver at the same end of link, through capacitive and inductive coupling, “hears” the signal.

Far-end crosstalk (FEXT) occurs when the transmitter sends a signal and a transceiver at the far end of the link, through capacitive and inductive coupling, “hears” the signal. FEXT will be of more concern in an asymmetrical system such as ADSL than symmetrical systems like HDSL. This is because strong signals originating from the near end, can interfere with the weaker signals originating at the far end.

What is the effect of noise?

Noise may be defined as the combination of unwanted interfering signal sources whether it comes from crosstalk, radio frequency interference, distortion, or random signals created by thermal energy. Noise impairs the detection of the smallest analog levels which may be resolved within the demodulator. The noise level along with the maximum clip level of an analog signal path set the available amplitude dynamic range.

The maximum data rate of a modem is limited by the available frequency range (bandwidth) and signal-to-noise ratio (SNR) which is amplitude dynamic range. If more of either is available, more bits may be transferred per second. The information carrying limit was discussed theoretically by Claude Shannon and is known as Shannon’s limit, or information theory.

xDSL modems take advantage of the spectrum above the telephone audio channel. While operating with somewhat less amplitude dynamic range they increase data rates by greatly increasing the frequency range of the communication signal (from about 10KHz to over 1.0MHz). To do this they require the installation of special equipment at the central office and customer premise.

What is a bridge tap?

A bridge tap is an accidental connection of another local loop to the primary local loop. Generally it behaves as an open circuit at DC, but becomes a transmission line stub with adverse effects at high frequency. It is generally harmful to xDSL connections and should be removed.

Extra phone wiring within one’s house is a combination of short bridge taps. A POTS splitter isolates the house wiring and provides a direct path for the xDSL signal to pass unimpaired to the ATU-R modem.

What are loading coils?

Loading coils are used to extend the range of a local loop for voice grade communications. They are inductors added in series with the phone line which compensate for the parallel capacitance of the line. They benefit the frequencies in the high end of the voice spectrum at the expense of the frequencies above 3.6KHz. Thus, loading coils prevent xDSL connections.
Testing DSL
Testing of DSL products using Trend products can take the form of field based installation or fault-finding assessment.

ADSL transmissions are affected through two key factors, external conditions and line properties.
External conditions which affect transmission include: Noise (conducted), Noise (induced/RFI), Cross-talk (Near/Far), Inter-operability, Line code (CAP v DMT), DSLAM/ATU-C settings.
Line properties cover: Balance, Load coils/taps, Hi Z/Lo Z, Non-uniform pairs, Pair length, Copper diameter.

How GOOD is the Copper?
It is vital that the DSL service provider knows the condition of the digital local loop in order to be able to provision a defined service level. When a subscriber requests an ADSL service, the provider needs to be in a position to state whether or not the service can be supported over the specific subscriber loop. This will depend upon the minimum service requirement (i.e. bandwidth) and the condition of the loop.

DSL Standards
European ETSI specification ETR 328 is the only current ADSL European standard in force and only covers loop and noise models. Additional specifications such as TS 101 388 for ADSL and TS 101 270 for VDSL are currently being developed by the ETSI TM6 workgroup. These specifications will also include requirements for electrical characteristics of the transceivers as well as loop and noise models.

The ITU-T G.99X.X series of standards provide design rules for the xDSL models and stipulate loop tests and noise injection models. They also contain electrical requirements for the transceivers including PSD masks for ADSL over POTS/ISDN and for systems providing reduced NEXT. They also provide for splitter characteristics.

DSLAM – Remote Modem
In the absence of established access performance requirements, various DSL vendors market their own remote CPE and CO exchange equipment. It is highly likely the two ends from one manufacturer will operate well together, but it is far from certain that, once mixed installations are involved, various manufacturers modems will interoperate.

Power Spectral Density
Power spectral density is the power expressed in dBms per Hz bandwidth. Limitations are accorded to the spectral profile of the PSD in a defined bandwidth in order to minimise the effect of crosstalk and therefore any destructive influence of the transmission on other services carried in the same bundle.

PSD masks will vary dependant upon the type of service provided. For example ADSL over POTS or ISDN will offer different potential for interference to the other service. Likewise full rate ADSL, G.Lite or VDSL occupy different proportions of the bandwidth and will therefore need to comply with different PSD mask limits.

Similarly, in an asynchronous transmission such as ADSL the upstream and downstream transmission occupies different areas of the transmission band and consequently PSD masks will differ for upstream (from ATU-R to ATU-C) and downstream (from ATU-C to ATU-R).

Power Measurements (ITU-T G.991.2)
Power measurements measure the power in the voice band and the power in the out-of band regions from the ADSL port. Since there should be no DSL signals transmitted in these regions both these power levels should be low.

Power in the voice band is measured as an average over the region from 0 to 4 kHz with the maximum value required to be less than 15dBm. Power in the out-of band region is measured over a sliding 1MHz bandwidth and is required to be less than –50dBm.

Longitudinal Conversion Loss
LCL measures the ratio of an applied longitudinal voltage (with reference to earth) against the measured voltage across a 100 ohm termination placed across the ADSL transceiver tip and ring.
If the HPF function of the POTS splitter is incorporated into the ADSL modem then the test is applied to the ADSL port using a 100 termination.

If the LPF function of the POTS splitter is also built into the ADSL modem then the test is repeated with the LPF POTS port terminated with impedances ZTC (000) and ZTR (600).

Return Loss of POTS and ADSL Line Ports.
Return Loss is essentially a indication of the degree of impedance matching of a connection. This matching is essential to achieve the best possible power transfer from one piece of equipment to another. Typically impedance matching of an ADSL Port is taken to be 100ohms. The POTS port is typically 600ohms for the UK.

And finally -The Acronym List. In no way intended to be definitive, but may help

ADSL – Asymmetric Digital Subscriber Line
ANSI – American National Standards Institute
ATM – Asynchronous Transfer Mode
ATU-C – ADSL Termination Unit – Central Office
ATU-R – ADSL Termination Unit – Remote
AWG – American Wire Gauge
BERT – Bit Error Rate Test
bps – Bits Per Second
BRI – Basic Rate Interface
CAP – Carrierless Amplitude and Phase
CATV – Cable TV
CBR – Constant Bit Rate
CLEC – Competitive Local Exchange Carrier
CO – Central Office
CODEC – Coder/Decoder
CPE – Customer Premise (or Provided) Equipment
CSU – Channel Service Unit
DCE – Data Communication (or Circuit-Terminating) Equipment
DLC – Digital Loop Carrier
DMT – Discrete Multi-tone
DSL – Digital Subscriber Line
DSLAM – Digital Subscriber Line Access Multiplexer
DSP – Digital Signal Processor
DSU – Data Service Unit
DTE – Data Terminal (or Termination) Equipment
EMI – Electromagnetic Induction
FDM – Frequency Division Multiplexing
FEXT – Far-end crosstalk
FTTC – Fiber To The Curb
FTTH – Fiber To The Home
HDSL – High bit-rate Digital Subscriber Line
HFC – Hybrid Fiber-Coax
IEC – Inter-Exchange Carrier
IEEE – Institute of Electrical and Electronics Engineers
ILEC – Incumbent Local Exchange Carrier
IP – Internet Protocol
ISDL – ISDN Digital Subscriber Line
ISDN – Intergrated Services Digital Network
ISO – International Organization for Standards
ISP – Internet Service Provider
ITU – International Telecommunications Union
IXC – Inter-exchange Carrier

Lets Get Technical About The Sheet Metal Brake & Tube bending

The machine that is called a sheet metal brake is used for metal working that will allow for sheet metal to be bent. Some machines allow for bends that are simple and simple creases, while others allow for forming pan and box shapes.

The various sheet metal brakes are:

The Cornice Brake uses a clamping bar that is solid and is as wide as the machine, but it can only make bends that are straight.

The Box and Pan Brake has a clamping bar that has several removable blocks. These blocks may be rearranged in order to allow bending in restricted areas on sheet metal as well as some that may already be partially formed. After bending the box or pan the completed item can then be screwed, soldered, welded, riveted or some other form of metal curving can be used.

The Bar Folder is a simple sheet metal break smaller than the cornice or the box and pan brakes. One handle makes the bend and clamps the piece with one motion. However, the depth is usually not as much as the cornice or the pan and box brake will handle.

The Press Brake is a more complex tool in that it forms the bend that are predetermined by clamping the piece between punch dies that match. It is generally made up of two C frames with are the sides of the brake. The C frames connected at the lower part to a table on a beam above which is movable. The upper tool is attached to the upper beam and the lower tool is attached to the table.

The Magnetic box and pan brake has a six ton magnet that is started with a foot pedal or with a button that will hold the steel clamping bar on the bar width or the bar length. It will hold down any configuration.
It will now be apparent that there are a multitude of bending brakes and in particular there is generally a sheet metal brake for sale that is ideal for each and every job.

The brake press uses either a hydraulic or servo electric method of operation. The servo electric mechanism is a device that is automatic and uses a sensor that gives negative feedback in order to fix the way the mechanism works.

The sheet metal bending brake of the type mentioned above can be had as manual or hand brake. In order to save you a lot of time with accurate measuring there is something called a back gauge. The back gauge is used to help you avoid the use of a tape measure when you are marking lines to line up with the nose bar. The back gauge has an inch and centimeter scale and a twenty five inch travel.

This is a useful time and labor saving device and while some brave hearted individuals might search for plans to make a homemade sheet metal brake, the vast majority will either hire the contraption or invest in a new machine.

If you only plan to do one specific job you might not think that you need to buy a new machine, but as prices of new models can be quite cheap it could be worthwhile making the investment. After all, if you look after the metal bending brake then you can always sell it on, along with any other sheet metal tools you own, in years to come. Tube bending

If finances are an issue or if you need a really expensive and powerful machine to do the job, then you could consider the option of buying a used sheet metal brake of some description.

With regards to bending sheet metal and in order to make sheet metal bending a little easier there is also the corner notcher which is hand operated. With a force of four tons it can notch sixteen gauge metals to a notch size of six inches by six inches.

If you are using a power punch press there are methods of safe guarding yourself or perhaps an employee that may be using the machine. These safeguards may range from putting up barrier to restraints.

The DIY enthusiast will be looking for something completely different to the commercial or professional user. While a DIY user might consider sheet metal brake rental or buying a used metal brake the frequent user would probably be looking to buy a new and unused machine for the job. Renewable construction methods are always preferred.

Whether you need a portable small sheet metal brake or something larger, with the right tool you’ll find the job is much easier to do.

Home or Bathroom Renovation: The power of colour

Tiling for your home or bathroom renovations is one of the best ways to make your home shine. You will most likely want to bring out certain aspects of your home or highlight features that are important to you. So what can you do when tiling to get the best out of your home? Have you considered trying different colors? You will have a lot of options to choose from so you will want to choose the best style for you. This isn’t too hard so here’s some thought that might help you to make your home renovation a success:

The power of colour

Colours can stimulate, heal, sooth or create a fun atmosphere. Are you the type of person who loves to have people over every second night or so? Or do you love those quite times reading a book on the couch? It’s important you know about stimulating and calming colours. How do you work out which colours are stimulating or calming?

Stimulating or Calming and why?

Try to imagine a 6 piece pie where every second piece has a colour. This will mean 3 colours which are yellow, red and blue. Now between these pieces what you can get by blending the colours on either side. Why is this important though? Stimulating colours are great for social areas while calming colours are great for quiet areas. So which colours stimulating or calming?


Anything between yellow and red is stimulating and to help your imagination you have colours that are within the orange, off white, or creamy range. Also, when either red or yellow is mixed with blue, it needs to have more red or yellow for it to be stimulating. Interesting, black is also stimulating.


Calming colours are achieved using the colour pie by mixing with blue. You can get some off whites on this side of the pie too along with grays and browns. White is also a calming tone.

The Different Types Of Sheet Metal Bending Brake

There are various metal working machines, but if you are working with sheet metal that has to be bent then you want to use a sheet metal bending brake.

There are two types of sheet metal bending brakes; the Cornice brake, will let you make simple bends and will let you make creases, while the box-and-pan brake, will let you make pan shapes and will allow you to make boxes. These are often called either bending machines or bending brakes.

The bending brake is a metal bender or sheet metal bender and it usually is a flat surface that is made to hold the material in place with a clamp that will come down and hold that material firmly in place while it is being bent. Your material can be clamped using the clamp manually, or with the use of a foot pedal.

The machine has a grate front that is hinged and can be lifted in order to force the material over an edge that is straight in order to make it bend to follow the plate. The angle up to which the bend can be made is one hundred and twenty degrees.

The Cornice Brake uses a clamping bar that is solid and is as wide as the machine, but it can only make bends that are straight.

The Box and Pan Brake has a clamping bar that has several removable blocks. These blocks may be rearranged in order to allow bending in restricted areas on sheet metal as well as some that may already be partially formed. After bending the box or pan the completed item can then be screwed, soldered, welded, riveted or some other form of metal fixative can be used.

The sheet metal bending brake machines come in various sizes such as the eighteen inch machine, the thirty inch machine, and the forty inch machine. You can get a large machine or a portable sheet bending brake to suit the many different uses.

Perhaps one of the most common sizes purchased is the 30 inch model. The 30 inch sheet metal bending brake for sale today can handle most jobs, and this is perhaps why it is so popular. Although other sizes might be more suited to either very small or very large tasks it seems that the 30 inch machine fits right in the middle.

The sheet metal brake machines can accommodate sheet metal from fourteen gauge to sixteen gauge and more. If you are looking to buy your sheet metal bending machine, rather then making your own, they can be purchased at any store that sells machinery, and they can be found online. The prices for the sheet metal bending machine range from fifty dollars to over two hundred dollars.

If you plan to build your own sheet metal bending brake or aluminum bending brake you can get your plans from various places on the internet. When you get to a website click on tools you can build which appears on the bottom of the list on the left hand side of the page.

It is difficult enough to build whatever thing you are looking to build, but building the tools with which to build that thing can also be difficult. If you are a true builder at heart then following sheet metal bending brake plans shouldn’t present a problem and certainly building your own tools will only add to the sense of accomplishment you feel at the end of a project.

The sheet metal bending brake bender is a machine that is not difficult to use but it somewhat wield construction may make it somewhat difficult to store, unless you are lucky enough to find and buy one that is collapsible for easy storage.

Why Do You Need A Bending Brake?

The first question you might ask is “just what is a bending brake?” and what sort of work function does it perform with metal.

The surface area of the bending machine is comprised in such a way that the metal is held in place with the downward action of the clamping bar so that there is no movement of it while the bending action is taking place.

The action of the clamping bar and bending may be manual, automatic and manage with either a foot pedal or hand bar.

The gate like front plate is usually hinged and can be raised in causing the metal to extend over a straight edge and it will bend to comply with the plate. Presently there are levers that open the brake’s clamp, which is a hefty flat bit of steel.

A person slides the piece of sheet metal inside of the clamp on the metal bending device, and then pulls the lever backwards to close the clamp that retains the sheet metal in place.

There is going to be an additional lever that’s fastened to the bending bar. You can move that lever up to the point it begins to bend the sheet metal. As soon as it gets to its preferred shape or angle, you’ll pull the lever to open up the clamp it will release metal.

There are several places where the sheet metal brake is of importance. Heating shops, car restoring fanatics, and aircraft builders, etc. This brake can be used to bend metal for car fenders, aircraft wings, heating ducts and all other sorts of parts.

Persons that do this sort of work really understand how hard it can be to bend all the required angles to the right shapes without the use of a bending brake.

You can easily purchase these bending brakes online. Some people however prefer to build their own sheet metal bending brake, and set about to do so. The reason that they might do this is to make the tool specific to their needs.

Also there are other factors to consider when choosing a metal bender, such as the type of metals to be bent. The gauge of it may affect the way the brake is constructed.

These metal brakes do have a lot of the same parts in them but just arrange different to do slightly different functions.

All in all, sheet metal bending would be very hard to do without the aid of a sheet metal bender.

There are a wide variety of bending machines for sale, and the use of a bending brake saves time and stress for the professional tradesman and DIY enthusiast too.

Conduit Bending Informational Resource

There are many types of conduit bending. I have seen many electricians who spent ages just trying to bend conduit.  Electrical conduit is a bending system which is used to protect the wires from damaging and thus protects the damaged wires.  They help in continuous grounding and anyone who comes in contact with them is often protected. You must know how to bend conduit only then you will be able to place it in the right spot.

When you are trying to bend a conduit you need to have a conduit bending, which means a bender of its size, a pencil and a measuring tape.  There are two main types of bending conduit which exist in the market, one is EMT conduit bending and the other is more rigid. The EMT conduit bending is said to be lightweight and thus is fairly easy to use. Both come in different sizes and thus can be chosen from a large variety that is available.  The sizes can range from half inch to quarter inch.

The first thing you need to know is how to bend the conduit. Bending conduit can be difficult but you can use a conduit bending guide for you help. It is likely that you will find a conduit bending guide inside which will guide you through you way to bending conduit. But if you don’t find it then you will a degree scale and arrow maker inside.  And on the same side would be a number most probably a number A, but moistly different companies have different conduit bending numbers.  The numbers are likely going to signify something, such as 5 is going to signify half inch while EMT 6 will signify ¼ inches of EMT conduit bending. This is called a deduct number.

When you are measuring you need to minus the deduct number from it only then the arrow will be inserted. Once you have subtracted the deduct number then you can mark it with the pencil. Make sure you place it alongside the arrow which you have marked. Place your conduit bending in line with the mark which you have created besides you arrow, you need to put pressure on it. Take the help of some professional if you need, other wise a steady foot pressure would be would be enough. You need to continue until you have bended you conduit up to 90 degrees.  There are different marks at 30, 60 and 90 degrees. You should keep putting on the pressure until you reach the 90 degree mark.  Then in the end you need to check whether you have placed your conduit bending right or not.  You need to check whether it is bending properly and the way you wanted it to bend. If its fits then it is a sign for your success.

I am certainly not saying that conduit bending is a piece of cake but instead it requires a lot of practice and skill, if you think you can’t do it then it is advisable to use the conduit bending guide I am sure that will be of a great help and you will be able to succeed in bending conduit.