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Investigation of Telecommunications Monitoring Capabilities for Intercepting DS-1
Communications Transmissions, 10-9094

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Principal Investigators
Michael W. Raschke (Mark Moczygemba)
David L. Buntin

Inclusive Dates: 08/26/98 - 12/26/98

Background - The Telecommunication Systems Analysis Position (TSAP) is a portable PC-based analog and digital telecommunications monitoring and analysis tool that uses custom modular Universal Telephony Interface (UTI) subsystems to monitor and analyze three different types of wired telecommunication protocols (not including DS-1). The digital DS-1 signals are much faster than the highest speed digital signals for which the UTI subsystems are designed. Therefore, the performance and synchronization requirements of the UTI subsystem are different for DS-1 signals. This project was based on investigating the interactions of DS-1 signals with the other signals on a UTI subsystem to determine if a UTI subsystem design change would enable the TSAP to monitor digital DS-1 communications transmissions.

Approach - The goals of this project were to determine the compatibility of the UTI subsystem with the DS-1 signals and to determine if a UTI subsystem design change would enable the TSAP to monitor and analyze the DS-1 signals. Minimal obsolescence of the existing UTI subsystems was desired. To accomplish these goals, a computerized DS-1 mockup test platform was developed that included signal and transmission channel simulators. Next, a prototype DS-1 interface module was developed using a microprocessor-based DS-1 evaluation circuit board. This circuit board and test platform were used to inject DS-1 signals from varying length- and quality-simulated transmission channels into the UTI subsystem. Finally, the performance of the UTI subsystem was determined by measuring the cross-talk attenuation of these DS-1 signals on adjacent signal lines on the UTI subsystem.

Accomplishments - Simulated DS-1 communication transmissions were generated and intercepted using the UTI subsystem and the prototype DS-1 interface module. Data errors in the intercepted data from the simulated transmission channels at both short and long (5,000 foot) lengths were virtually nonexistent to the extent that the reproduced voice transmission was extremely clear to the human ear. Additionally, the UTI subsystem exhibited a cross-talk attenuation of the signals on adjacent signal lines of at least -60 decibels, which is a level well below that which would cause adverse operation of the UTI subsystem. The UTI subsystem microprocessor experienced no data throughput bottlenecks that might significantly affect the design requirements for a UTI subsystem design change to enable the DS-1 interception capabilities.

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