Line Testing via Periodic Voltage and Current Measurement
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Solution Overview
Problem
Current line testing methods in communication networks face challenges in accurately determining the presence of terminal devices and signatures on communication lines, particularly in distinguishing between on-hook and off-hook states, and identifying DSL modems without disrupting service or causing false readings.
Innovation Solution
A method involving the application of varying voltages on communication lines to measure currents at different times, using the non-linear characteristics of terminal device signatures like Zener diodes to determine the presence of terminal elements and modems, and employing existing line cards with SLIC and CODEC capabilities to perform these measurements without additional hardware.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If voltage is applied to the communication line to measure current for detecting terminal devices, then detection accuracy is improved, but service disruption risk increases
Solution Approach 1:
The patent applies voltage in periodic intervals rather than continuously. A test voltage is applied only during designated test periods when no voice traffic is occurring, allowing accurate current measurements for terminal device detection while minimizing service disruption. The system alternates between test periods and normal service periods.
Solution Approach 2:
The patent uses an intermediary testing mechanism that interfaces with the existing SLIC (Subscriber Line Interface Circuit) infrastructure. The test voltage is applied through the existing line card hardware, and current measurements are taken through the same path, allowing detection without requiring separate test equipment that would disrupt service more significantly.
2Reliability
If multiple current measurements at different time points are performed, then detection reliability is improved, but measurement time increases
Solution Approach 1:
Multiple current measurements are performed during periodic test intervals rather than requiring continuous measurement time. The system applies voltage and takes measurements at multiple time points within each test period, then waits for the next test period to repeat the process. This periodic approach achieves reliable multi-point measurement without proportionally increasing total time loss.
Solution Approach 2:
The patent maintains continuous readiness for testing by keeping the measurement system active and prepared. During service periods, the system continuously monitors line conditions and prepares measurement circuits, so when test periods arrive, measurements can be taken immediately without additional setup time. This continuity reduces the effective time loss between measurements.
3Device complexity
If existing line cards with SLIC are used for testing, then device complexity is reduced, but measurement precision may be compromised
Solution Approach 1:
The patent makes the existing SLIC line card hardware universal by enabling it to perform both its original voice traffic handling function and the additional function of test voltage application and current measurement. The same physical hardware (line card, SLIC circuitry) is used for both service and testing, eliminating the need for separate dedicated test equipment while maintaining measurement capability through proper signal conditioning and measurement circuits already present in the SLIC.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach allows for accurate detection of terminal devices and DSL modems, reducing the risk of service disruption and improving the frequency and cost-effectiveness of line testing by leveraging existing infrastructure.
Implementation Method 1
using the non-linear characteristics of terminal device signatures like Zener diodes to determine the presence of terminal elements
Data Source
AI summary
A method of testing a communication line includes applying a voltage as a function of time on the communication line and measuring at least a first current and a second current flowing via the communication line. The second current is measured at a different point in time than the first current. The method includes deciding whether a given terminal element is connected to the communication line based on the first current and the second current.