Measurements of Echo Parameters Pertinent to High-Speed Full-Duplex Data Transmission on Telephone Circuits

Approximately 400 sets of field measurements were made on public switched telephone network connections from a location in Canada, to two locations in Australia and to 11 locations spread across the United Kingdom, to observe the properties of echos pertinent to high-speed full-duplex voiceband data transmission. The observations have been analyzed to give statistics on the duration, delay, and level of talker echo. Also, results on listener echo are included. The stability of echos is important in the design of echo cancelling and full-duplex digital transmission equipment, and so data are presented on the modulations of the echo or the phase roll that was observed and their stability. Results are included for calls placed over both cable and satellite circuits.