04918623 is referenced by 51 patents and cites 20 patents.

Apparatus for testing the performance of a communication line that carries customer data between two modems, including a programmable processor (for example, a digital signal processor) in each modem that either performs modulation or demodulation of customer data or tests the line, and a controller (for example, a programmable host processor) that switches the programmable signal processor selectively between processing customer data and line testing. The communication line carries both customer data and network control commands that include a test command for initiating testing, and each host processor responds to the test command by switching the signal processor to the test mode. There are a plurality of modems forming a data network and a central network control system connected to the network for providing the test command. The test command names two of the modems to participate in the testing and the controller identifies whether a given modem is one of the participants. The controller causes all of the modems to cease processing customer data while the testing is in progress. The network carries progress signals while the testing is in progress. The controller causes all modems other than the two modems to monitor the network for the progress signals and to again process customer data when the progress signals cease to appear.

Title
Testing the performance of a communication line between two modems using modem processor
Application Number
784212
Publication Number
4918623
Application Date
October 19, 1988
Publication Date
April 17, 1990
Inventor
Bruce C Giese
Rockland
MA, US
Robert M Wilson
Walpole
MA, US
Kelly A Lyndon
Boston
MA, US
John A Lockitt
Sherborn
MA, US
Agent
Fish & Richardson
Assignee
Codex Corporation
MA, US
IPC
G06F 11/00
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