Based on DSP technology, the tester achieves accurate and repeatable results by implementing all G.168 test procedures digitally. Signal injection and monitor points are provided, allowing analogue measurements to be made if desired.
The software is a Windows 9X-based software package designed to perform real-time subjective and objective tests for all commercially available Echo Cancellers.

 

DSPG's ECT-1 is housed in either in a 10" mini case, a portable 3U case, or a 19" rack. Based on advanced DSP technology, the tester achieves accurate and repeatable results by implementing all test procedures digitally. Fully self-contained, each unit includes a built-in single board computer and hard disk drive, only requiring the addition of the echo canceller under test, a keyboard, mouse and monitor. For field use, a mini version of the portable 3U case is also available. A laptop computer can be connected in place of the peripheral devices.

Features
G.168 tests of all commercially available Echo Cancellers at a click of a mouse. Includes customized drivers for each Echo Canceller to automate the testing process Flexible DSP based hardware allows upgrades up to full Network Emulation Allows standard subjective tests Stores graphical and audible output of tests Output of tests can be viewed on any computer using Viewer software Generates Pass/Fail test report Continual updates of tests and drivers via Internet Automated Perceptual Analysis Measurements, "Objectively subjective" Automated G.164/165 tone disable testing Records Send & Receive channels of live network traffic Stand-alone/remote controlled via laptop Buildable model of network [screen shot]

ECT Concept
One of the key factors for improving the quality and performance of PSTN networks are Echo Cancellers. However, with so many models on the market there is inevitably a varying degree of performance There is now an obvious need for purpose designed instruments such as the ECT1 that allow an easy and automated range of tests including G.168 2002 and G.168 2000. Due to the differences in the individual cancellers operations, special drivers agreed with manufactures should be used to provide the most optimal test conditions.

Objective G.168 2002 Test Mode
All the tests are implemented by the software, which is divided into several separate modules, such as, an echo path generator with three independent branches, two signal generators able to generate Composite Source Signal (CSS), tones, fax sequences or noise and a measurement instrument.

G.168 2000 & 2002 Testing [screen shot]
After a simple configuration procedure, the ECT1 is able to perform the G.168 tests without any user interaction. The ECT1 controls the echo canceller parameters (Convergence, H register, NLP), generates all of the test signals, measures the output and processes the results. At the end of the test session, the user can check the results using either the graphic viewer or by printing out a detailed report. All software may be continuously upgraded following any new versions of the G.168 specification including G.168 2000 and G.168 2002.

PAMS & Noise Reduction Testing [screen shot]
The Perceptual Analysis Measurement System is a new addition to the ECT1 test suite. Originally designed by BT Laboratories, this algorithm analyses the quality of a signal for degradation and gives a subjective MOS or Percentage of Toll Quality score as related to the human ear. Percentage of Toll Quality is a result that shows how good a call is compared to optimal network conditions. Effectively making subjective testing, objective.
This can also be used for testing of Noise Reduction algorithms. This operates by inserting noise just before the echo canceller and analysing the effectiveness to return to the original reference file.

G.165/G.164 Tone Disabler Testing [screen shot]
In a package similar to G.168 or PAMS, this tests the tone disabling ability according to G.165 and G.164. The tolerance limits for many different parameters are tested, for example, frequency range, angle of phase reversal, period of tone, signal/noise ratios and many others. This will give an accurate description of the tone disabling capability of echo cancellers.

G.169 Automatic Level Control [screen shot]
Following our standard software design, this tests the automatic level control ability of echo cancellers. Many different tests are implemented including ALC in the presence of echo or noise, DTMF tests and standard ALC stability tests. Testing ALC devices will give you confidence that you will not see a pumping effect in the network and that the device is working.

Subjective Testing Mode [screen shot]
Using the dialogue boxes the user can manipulate the echo path generator with its three independent branches and listen to the effects using the four-wire TEL-4 telephones or a microphone and loudspeakers. A central office card can also be connected which will allow you to test standard two-wire telephones or fax machines. You are able to set-up line conditions and analyse the effect in real world situations. The echo canceller parameters can be set up manually via a plug-in keypad or from the ECT-1 software via a V.24 serial port. Optionally, the echo canceller can be controlled directly via a parallel port of the PC. The tests used within G.168 are objective and are not intended to replace or eliminate the use of subjective tests when measuring the perceived quality of echo cancellers. The ECT-1 allows the user to continue testing using the subjective method.

Non-Intrusive Monitoring [screen shot]
When put into a non-intrusive monitoring mode the ECT can record data in wave files. These wave files can then be used in conjunction with Analysis software to measure SV6 levels, psofometric noise, delay and ERL of a network. The advantage of this is being able to prove that an echo canceller has improved the voice quality of your network

Network Connectivity
The ECT can be used in either a terminate or bridge mode when connecting to switches or similar devices. This allows testing and analysing of many devices in the network. In the bridge mode you can also use the ECT to insert delay into the system.

Future Development
The ECT is constantly being upgraded and new features added to it. All additional modifications will only be software that can be downloaded from the downloads section or sent via email. We are currently working on a four point recording system for enhanced non-intrusive recording. We also make custom designed software for individual customers needs and desires.