Q.	Why should xDSL Service Providers and xDSL Rollout Managers use NETLINK 430 Digital Line Test Sets?
A.	Here are a few of the ways that NETLINK 430 DLTS can assist Network Service Providers to ensure that a high standard of quality and reliability is maintained to customers in the deployment of high speed Digital Subscriber Line (xDSL) services. The Test Set increases the productivity of field staff, and reduces the costs of testing Automatic remote controlled operation means that ONE field technician can now perform tests in a fraction of the time which previously required two technicians Automated test results mean significant reductions in paper work, recording and administration, and are free from misinterpretation or human error Complete cable performance data eliminates the need for retesting as xDSL services are upgraded or as new services are deployed in the future The ability to completely characterise each cable pair and detect marginal faults which otherwise lead to repeat service calls and customer dissatisfaction The Test Set can replace a range of normal test instruments, thereby allowing Service Providers to reduce the inventory and costs of test equipment.
Q.	Why test at all? Why can't we just determine which subscriber lines will support different xDSL services, from our existing cable records and/or by geographic distance from the exchange?
A.	You can, but in the longer term, not testing can turn out to be false economy. Cable records are not always accurate. Individual cable defects, such as split pairs and bridged taps, can significantly degrade xDSL transmission, compared with a "good" pair of the same length and in the same cable. A defective, for example, unbalanced cable pair can appear to perform OK initially, but later become unreliable as more xDSL services are commissioned in the same cable. Resulting repeat service calls and customer dissatisfaction can be expensive. You can use your test data to improve your cable records, to supplement your prequalification data, and to identify potential problem areas. NETLINK testing completely characterises the performance of each cable pair for ALL xDSL services. Once done, you won't need to return, as more demanding, higher speed xDSL services are rolled out in the future. The NETLINK DLTS can identify most commonly occurring cable defects which can degrade xDSL, by single ended tests, e.g. from the exchange MDF. A single field operator can test many subscriber lines in a short time, without travelling, and the test results will be valid for all future xDSL.
Q.	Why can't we use xDSL modem based testers?
A.	You can, and you can also use the similar diagnostic capabilities built in to DSLAMS, or you can get your customers to use the similar diagnostic capabilities built into their xDSL modems. The xDSL Modem Tester method is fairly common in the U.S.A. But again, an unbalanced cable pair can appear to pass initial modem diagnostics but can later become unreliable as xDSL data rates are pushed up, and more (and often deregulated) xDSL services are deployed in the same cable. There are many similarities to the technique of field technicians using an Internet V-Series Modem to diagnose customer problem with modem speed, errors or disconnect problems. Whether or not the technician's modem works correctly, does not lead directly to the cause of the problem, nor the actual network fault, nor to customer satisfaction. When technicians have performed NETLINK DLTS tests (from the customers premises or from the exchange) they know: The performance of the customer's line (relevant to all xDSL) Its loss and/or effective length Whether the pair has any defects What those defects are.
Q.	Why was the NETLINK 430 Digital Line Test Set developed?
A.	Prior to the development of the NETLINK 30 DLTS, the only xDSL test tools were manually operated wideband oscillators in conjunction with wideband level meters, plus a variety of the test gear such as high voltage "Meggers" etc. These generally required a skilled technician at each end of the cable, and the results were prone to human error and misinterpretation. Testers dedicated to specific xDSL testing e.g. for ISDN or HDSL and/or emulating xDSL modems also appeared on the market. EDL took the view that xDSL service providers would need test equipment which: Was simple to use , even by minimally trained field staff Could identify cable defects, even if they did not appear to degrade the xDSL service currently deployed Could completely characterise the performance of cable pairs for all xDSL services (current and in the foreseeable future) Would enable xDSL service providers to automate the acquisition of xDSL and cable test data Would minimise "truck rolls" e.g. by providing single ended testing (without field staff having to travel to the far end of the cable). The NETLINK 430 DLTS has successfully achieved these goals and has enabled xDSL service providers in more than 15 countries to perform automated, single person xDSL testing. The NETLINK 430 DLTS: Is extremely simple to use (e.g. typically all the user has to do is press the test button, and wait for 1 minute or less for the DLTS to display "Passed" or "Failed" Identifies cable defects such as loading coils, bridged taps, split pairs, unbalanced pairs, HR joints and wet cable sections, which can degrade the reliability of currently deployed or future xDSL services Completely characterises the performance of each cable pair for all xDSL services. Once a series of DLTS tests have been performed and the results stored away, service providers do not need to access the pair again to determine if it is suitable for SDSL or VDSL or any other xDSL in the future DLTS test results can very simply be downloaded into service provider's specialised databases or standard 3rd party databases and spreadsheets. The tests required to be performed, the test parameters and the limits to be applied to the tests (e.g. for different xDSL categories) can also be downloaded from a PC to the NETLINK DLTS Most cable defects, and the effective open circuit cable length (i.e. determining the loss) can be measured by single ended tests, performed by one person, without having to leave the telephone exchange.
Q.	Why should I (an end user/field operative) use the NETLINK DLTS? What's in it for me?
A.	You will find it easy to use. It has been readily accepted by end users in many countries around the globe, for that very reason. Your management probably expects you to be multi-skilled with minimal training. You will find that performing xDSL tests with the NETLINK DLTS is a skill which you can easily pick up. Its use will make you much more productive, and thereby a more valuable employee. You will single handed be able to test pairs and find problems in a fraction of the time (often without even leaving the exchange) which two people would take using other test methods. The NETLINK DLTS will enable you to identify problems on the spot , and therefore minimise customer dissatisfaction and unnecessary repeat service calls , either by yourself or by your colleagues. You will become a better Network detective.
Q.	How do I use NETLINK 430 DLTS?
A.	Most of the time, your DLTS will already be in the right testing mode, and will be pre-programmed to perform exactly the tests you need to do, and what limits to use for each test. So, all you need to do is : Plug the Test Lead into the Tester (this automatically turns it on). Connect the Test Lead to the pair you want. Press [Auto] and [Test]. The DLTS will then perform the preselected tests and display PASS or FAIL. You can step through the individual test results, if you want, by pressing [] and [‚]. Or you can download them to a computer, for subsequent storage and analysis, by pressing [DOWN] and [TEST].
Q.	What are the most commonly occurring cable pair problems which can degrade xDSL services?
A.	The most usual are pair defects which cause little if any problem for POTS use, but can significantly degrade xDSL , such as spilt pairs and bridged taps. With a typical subscriber pair containing up to 20 randomly jointed connections, split pairs can easily occur and remain undetected until xDSL is required to operate over the pair. Some surveys have shown that more than 50% of existing customer cable pairs have one or more bridged taps (i.e. forgotten remnants of previous customer connections). Other relatively common faults which the DLTS finds include dry joints, insulation problems (e.g. wet cable sections) and unbalanced pairs (leading to noise and crosstalk).
Q.	What is xDSL?
A.	It is a generic term for a range of Digital Subscriber Line (DSL) services such as ADSL, HDSL and VSDL. Some of them such as ADSL are Asymmetric (i.e. the download data rate to the customer is much higher than the upload rate); others are Symmetric (e.g. SDSL). In general they use digital signalling techniques to transmit data (including Voice over Internet Protocol) to and from the customer. Mainly they use complex digital signalling processing for modulation and demodulation (modem) techniques to carry high data rates over relatively small bandwidths (e.g. typically 8 Mbps over 1MHz for ADSL). These techniques also usually distribute the data over a broad band to minimise the effect of crosstalk and electromagnetic interference, such as AM broadcast stations. The DLTS User Guide and Training Course both contain additional information on different types of xDSL.
Q.	What is meant by the "crosstalk environment"?
A.	Crosstalk problems are minimal during the early deployment of DSL. This means that xDSL can be provisioned on cable pairs which are prone to radiating and picking up crosstalk (and other interference) due to unbalance . However, in a highly competitive market place between competitive carriers, service providers and xDSL equipment suppliers, and with increasing deployment of faster and more "aggressive" xDSL services, interference between cable pairs is becoming an increasingly difficult problem. This is often referred to as the "crosstalk environment", where the levels of interference often exceed signal levels. The NETLINK 430 DLTS can significantly assist in these problems with the increasingly digital and unregulated "local loop". The DLTS directly measures pair unbalance, which is the basic cable impairment leading to crosstalk and interference problems. It also measures near end (NEXT) and far end (FEXT) crosstalk as well as signal to noise ratio. The DLTS can also non intrusively measure the signal levels and frequencies present on a cable pair, to enable network providers to determine what services competitive carriers are deploying on their network, in an unregulated environment. The NETLINK 430 DLTS will continue to operate with negative signal to noise ratios, i.e. where the noise (interference) levels exceed the signal levels.
Q.	How do I switch on the DLTS Meter and Transponder?
A.	Simply plug in the appropriate Line Test Lead.
Q.	What do I do if nothing happens?
A.	This usually means that its battery needs changing. (Refer to the Trouble Shooting Section in your User Guide). Or you may not have plugged the Line Test Lead in far enough, or it might be plugged in upside-down. (It is polarised with a square key, but it can be forced the wrong way.)
Q.	What do I do if the Transponder flashes its LED indicator when I switch it on?
A.	If it is the green indicator flashing, this means that the battery needs charging. If the yellow or red indicator is flashing, check that the Line Test Lead is not shorting or connected to anything when you plug it in. Otherwise flashing yellow indicator can mean that the Transponder calibration has drifted e.g. from being stored in a closed vehicle in hot sunlight. Let the equipment settle to between 5oC and 40oC, and then try again.
Q.	What if the Meter displays "No Transponder"?
A.	Either the Transponder is not connected, the Meter is connected to the wrong pair, or the pair is open or short circuit, or for some reason has too much loss for the two ends to communicate. Use the Transponder Trace Tone to trace the cable pair.
Q.	What do I do if the Meter displays 'CAL FAULT' or 'CAL FAIL'?
A.	Check that its temperature has settled to between 5oC and 40oC (i.e. not freezing or very hot to touch). Perform Auto Calibration (refer to the User Guide for details on how to do this). If the Meter continues to display 'CAL FAIL' after repeated Auto Calibration, you need to contact Technical Support (e.g. tech.support@edlaus.com).
Q.	What is the cause of severe 'ripple' in the high frequency response of the pair (i.e. between 100 KHz and 1 MHz)?
A.	This is almost certainly caused by bridged taps. These cause anomalous losses at frequencies where the length of the lateral is a multiple of half wavelengths at the test frequency. The loss of a defect free, unloaded cable pair should increase steadily with frequency, and is directly proportional to its length. (Refer to the User Guide or Training Course for more information.)
Q.	How do I interpret test results?
A.	The easiest way is to compare the test results of a pair with the test results of a "good" pair. Any pair which gives significantly "worse" results than other pairs of the same length is immediately suspect. The other technique is to compare the test results with the results you expect from the length and gauge of the pair. The Utility disk supplied with each unit contains a "Cable Model" which helps you to do this. Remember that the loss (at any frequency) and the capacitance of a pair is directly proportional to its length. (Refer to the User Guide or Training Course for additional information.)
Q.	How do I download Test Results and upload preselected Test Parameters and Limits?
A.	The quick answer is that you press [DOWN] and [TEST] to download, or [UP] and [TEST] to upload. The User Guide and Utility Disk supplied with each DLTS contain additional information to help you to connect the instrument to your PC (if you have problems with this), and to transfer data between the instrument and your preferred database or spreadsheet program.
Q.	How do I find my way around the different tests which the DLTS can perform?
A.	You can press [AUTO] and [TEST] to perform all the preselected tests of your choice. Or you can select any group of tests (e.g. Noise Tests) and then press [TEST] to perform all the Noise Tests. Or, for specific fault finding, to select the group of tests you want, then press[] and [‚[ to select the particular test you require. You can also press [EXIT] at any time to get you back to the main Select Test menu.
Q.	Is technical support available for the DLTS?
A.	Anywhere, anytime. Email tech.support@edlaus.com or fax +61 3 9762 3640 in the first instance, for immediate assistance or advice. Please feel free to use the same contact for any other input, or for assistance with any other needs.