Telephonic communications – Diagnostic testing – malfunction indication – or electrical... – Using portable test set
Reexamination Certificate
1998-12-07
2001-04-10
Nguyen, Duc (Department: 2643)
Telephonic communications
Diagnostic testing, malfunction indication, or electrical...
Using portable test set
C379S003000, C379S008000, C379S008000
Reexamination Certificate
active
06215854
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates in general to communication systems, and is particularly directed to a new and improved digital signal processor-based craftsperson's test set, that operates in two modes: 1- terminal mode—in which the test set functions in the place of customer premises equipment (CPE); and 2- line monitor mode—in which the test set is connected to the line under test and monitors data signals being transmitted to and received from an existing CPE. In both modes the test set has the ability to not only analyze and display the data being sent to and from the CPE, but also parametric information about the signals being sent.
BACKGROUND OF THE INVENTION
For testing and troubleshooting purposes, telephone network field service personnel, or craftspersons, have conventionally employed what are essentially ruggedized versions of a standard telephone handset. As such, the functional capabilities of these conventional test sets are not adequate to handle an ever expanding number of aspects of today's telecommunication environment, including, but not limited to, special features, such as call-waiting, caller ID, and the use of POTS (plain old telephone service) lines to deliver digital data services. In addition, because the acoustic interface of a conventional test set is essentially a half-duplex architecture, the field technician's ability to use it in a ‘hands-free’ manner can be severely limited, especially in an environment having high ambient noise, such as that inherent in the operation of industrial equipment and the flow of highway traffic.
As a consequence, there is a need for an improved test set, which retains the capabilities and physical characteristics of a conventional test set (namely, one that can test POTS lines, and is relatively compact (hand held) and physically and electrically robust), yet enables the craftsperson to monitor, receive and process signals of a variety of formats that may be present on a line under test. Moreover, field personnel have expressed a desire that their test sets have a truly ‘hands-free’, full-duplex, dual direction acoustic interface or speakerphone, namely, one that allows the field technician to talk (from a distance) in the presence of background noise, while simultaneously listening to an acoustic output being generated by the test set's receiver.
SUMMARY OF THE INVENTION
In accordance with the present invention, the above-described objectives are achieved by a new and improved digital signal processor-based test set, that is configured and programmable to perform a variety of signal processing functions, including, but not limited to, performing conventional test set operations, providing effectively real-time, full-duplex speakerphone communications, and the processing of user feature analog modem signals. Such user feature signals may include caller-identification signals, visual message waiting indicator signals, and analog display services interface signals. The digital signal processor (DSP)-based test set of the present invention also has the ability to measure electrical conditions (on-hook and off-hook voltage, and off-hook current) of a telephone line. It can measure the line's response to an electrical stimulus, so as to enable the test set to detect the presence of an electrical discontinuity, such as a load coil, that has been inserted in the line.
The signal processing architecture of the digital signal processor-based test set of the present invention preferably includes a telecommunication link connection port, through which the test set may be connected to (tip and ring conductors) of a standard two-wire pair POTS subscriber line. A tip/ring interface, which serves as a POTS loop current load, couples audio (voice, ringing, tone) signals to and from the POTS line connection, and allows loop power to be derived from the POTS line for an internal loop-powered supply for operating the circuitry of the test set.
Incoming voice and tone signals from the POTS line are digitized by a line-associated codec and coupled to a supervisory control digital signal processor (DSP), which is programmed to process signals received from the line and which have been digitally formatted by the line codec for delivery to a user interface (input/output unit). The DSP is also operative to process inputs from the user interface unit for application to the line. Outgoing signals to be transmitted over the network, as supplied from the DSP, are converted into analog format by the line codec and applied to line via the tip/ring interface.
A monitor mode circuit is coupled to the line connection port to enable the line to be monitored for the presence of audio signalling without having to go off-hook. A data detector is coupled to the line connection port to determine whether data signals are present on the line, and thereby prevent the test set from going off-hook and corrupting a data signal, if in fact a data signal detected on the line.
The user interface unit allows the craftsperson to input and receive information signals associated with the operation of the test set, or to input and receive voice signals during full-duplex communications with another party coupled to the line. For this purpose, the user interface includes a keypad, an LCD visual display, and an audio interface through which the craftsperson may listen to and vocalize acoustic signals into the test set. The audio interface is coupled to the processor by means of an audio-associated codec.
In order to provide effectively real time, full-duplex, dual-direction communications, which allow the field technician to talk (from a location within the sensitivity range of the test set), while simultaneously listening to an acoustic output generated by the test set's receiver, the test set's processor is programmed to execute an echo canceling routine that suppresses a replica or echo of the acoustic signal that has been sourced from the far end of the line and has reentered the test set's microphone from its output speaker, or is coupled into the line as a result of impedance mismatches in the electrical interfaces.
To accommodate signals simultaneously sourced from each end of the network, the echo cancellation routine contains a pair of ‘mirrored’ or complementary echo cancellation software modules. A line (network) echo cancellation module processes signals in the signal paths with the line interface and is operative to prevent ‘near end’ audio signals input from the test set microphone from being injected as electrical echoes into the audio signals output from the speaker. An acoustic echo cancellation module processes signals in the signal paths of the test set's microphone and speaker and is operative to prevent ‘far end’ audio signals from the network from being injected as acoustic feedback echoes into the audio signals outbound to the network.
The full-duplex speakerphone processing routine is initialized in a half-duplex mode, allowing audio signals to be transmitted in only one direction at the time. Whichever audio signal has the higher signal level will control the signal path to be suppressed. During this initial half-duplex conversation between the craftsperson and the far end of the network, each of the echo cancellation modules trains an associated echo model. As the line and acoustic echo models are trained, the amount of gain reduction of the originally gain-suppressed signal path will be decreased, until the processing routine eventually reaches what is effectively a full-duplex mode of operation. The echo models are continuously adjusted during further audio signal processing. Should the performance of the echo canceler degrade below a threshold that effectively prevents simultaneous audio communications, the routine reverts back to half-duplex mode, in which gain of a respective signal path is controlled by audio level, as in initialization mode. Then, as the echo models are retrained, the processing routine again reaches full-duplex mode.
In addition to providing real time, f
Allen Dyer Doppelt Milbrath & Gilchrist, P.A.
Harris Corporation
Nguyen Duc
Taylor Barry W
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