Telephonic communications – Diagnostic testing – malfunction indication – or electrical... – Testing of subscriber loop or terminal
Reexamination Certificate
2001-02-08
2003-02-18
Nguyen, Duc (Department: 2643)
Telephonic communications
Diagnostic testing, malfunction indication, or electrical...
Testing of subscriber loop or terminal
C379S029030, C379S029040
Reexamination Certificate
active
06522723
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a telephone line tester and, more particularly, to a telephone line tester which can be positioned close to customer telephony equipment and communicate test results to a test controller positioned remote from the customer telephony equipment.
2. Background Art
Heretofore, customer telephony equipment was connected to a switch via copper wire pairs. The switch enabled telephony equipment of one customer to be connected to telephony equipment of another customer connected to the same switch or to another switch connected thereto. In order to test the customer telephony equipment, test equipment connected to the switch was connected thereby to a select one of the customer telephony equipment. Selectively connecting the customer telephony equipment thereto enabled the test equipment to test the customer telephony equipment for proper operation.
The inherent resistance of the copper wire pairs utilized to connect customer telephony equipment to the switch limited the effective distance of the connection between each customer telephony equipment and the switch. This limitation required numerous interconnected switches to be distributed throughout a service area to provide telephony service to customer telephony equipment in the service area.
To increase the distance between the switch and each customer telephony equipment, a digital loop carrier system can be positioned between the switch and the customer telephony equipment. The digital loop carrier system enhances the service area of each switch by providing a digital communication network for carrying telephony signals digitally over a significant portion of the path, for example, via a fiber optic cable, between the switch and one or more customer telephony equipment. The digital loop carrier system converts electrical signals transmitted on each copper wire pair into optical signals that can be transmitted over longer distances than the inherent resistance of each copper wire pair would permit. Customer telephony equipment positioned close to the switch can be connected directly thereto.
A problem with the digital loop carrier system is that it is necessary to connect a copper bypass pair in parallel with the fiber optic cable to facilitate testing of the customer telephony equipment. One end of this copper bypass pair is connected to a pair gain test controller which is connected between the test equipment and the switch. The other end of the copper bypass pair is connected to an end of the digital loop carrier system opposite the switch for connection to customer telephony equipment. The pair gain test controller enables the test equipment to be selectively connected to customer telephony equipment connected to the end of the digital loop carrier system opposite the switch via the copper bypass pair or to customer telephony equipment connected directly to the switch via a copper wire pair. Problems with the copper bypass pair running parallel to the fiber optic cable include the susceptibility of the copper bypass pair to corrosion and breaking over time, variances in resistance of the copper bypass pair due to changes in temperature, the need for the test equipment to compensate for the increased distance between the test equipment and the customer telephony equipment and reduced testing accuracy due to electrical impairments occasioned by the copper bypass pair.
It is, therefore, an object of the present invention to provide a low cost and flexible telephone line tester which can be positioned at an end of a digital loop carrier system adjacent customer telephony equipment and which can be utilized to test the customer telephony equipment in a manner similar to test equipment heretofore positioned adjacent the switch side of the digital loop carrier system. It is an object of the present invention to avoid the use of a copper bypass pair in parallel with a fiber optic cable in order to test customer telephony equipment. Still other objects of the present invention will become apparent to those of ordinary skill in the art upon reading and understanding the following detailed description.
SUMMARY OF THE INVENTION
Accordingly, I have invented a telephony test system for testing customer telephony equipment. The telephony test system includes a test control computer configured to supply an electrical test request signal and to receive an electrical test result signal. A central office terminal is connected between the test control computer and a fiber optic cable. The central office terminal is configured to receive the electrical test request signal from the test control computer, to convert the electrical test request signal to a corresponding optical test request signal and to supply the optical test request signal to the fiber optic cable. The central office terminal also receives an optical test result signal from the fiber optic cable, converts the optical test result signal to the electrical test result signal and supplies the electrical test result signal to the test control computer. A remote terminal is connected between an end of the fiber optic cable opposite the central office terminal and telephony equipment of a plurality of customers. The remote terminal is configured to receive the optical test request signal from the fiber optic cable and to convert the optical test request signal to the electrical test request signal. The remote terminal also receives the electrical test result signal, converts the electrical test result signal to the optical test result signal and supplies the optical test result signal to the fiber optic cable. A line test unit (LTU) has a controller between the remote terminal and a high voltage amplifier configured to be connected by the remote terminal to select customer telephony equipment to supply a test signal thereto. The LTU includes a power supply configured to be controlled by the controller to supply electrical power to the high voltage amplifier. The controller causes the high voltage amplifier to supply a test signal to the customer telephony equipment. The controller determines electrical power dissipated by the high voltage amplifier supplying the test signal to the customer telephony equipment and controls the power supply to adjust the voltage supplied to the high voltage amplifier to avoid electrical power dissipated by the high voltage amplifier from exceeding a desired maximum electrical power dissipation.
The power supply can supply to the high voltage amplifier a differential voltage having a maximum value of ±190 volts. The controller can include a digital signal processor (DSP) operating under control of a software program and a logic circuit controlled by the DSP, with the logic circuit or the DSP implementing a communication interface which receives the electrical test request signal from the remote terminal and which supplies the electrical test result signal to the remote terminal.
The LTU can include a digital-to-analog converter (DAC) to receive digital signals from the controller and to produce an analog signal as a function of the received digital signals. A successive approximation network can be connected to receive the analog signal from the DAC, to compare the analog signal received from the DAC with a measured electrical condition of the customer telephony equipment and to provide to the controller a binary signal indicative of the comparison. A receive channel filter can filter the measured electrical condition and supply the filtered and measured electrical condition to the successive approximation network for comparison. A sample-and-hold switch network can receive the measured electrical condition and supply the measured electrical condition to the successive approximation network for comparison. The controller connects the successive approximation network to selectively receive the filtered and measured electrical condition from the receive channel filter and the measured electrical condition from the sample-and-hold switch network.
The LTU can include
Nguyen Duc
Tollgrade Communications, Inc.
Webb Ziesenheim & Logsdon Orkin & Hanson, P.C.
LandOfFree
Telephony line test unit and method does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Telephony line test unit and method, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Telephony line test unit and method will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3181955