Michael E Dugan

US Patent:

46882090, Aug 18, 1987

Filed:

Nov 27, 1984

Appl. No.:

6/675121

Inventors:

Frederick J. Banzi - Andover MA
Michael J. Dugan - Merrimac MA
Randolph W. Johnson - Northbrook IL
Douglas D. Saylor - Naperville IL
Craig A. Sharper - Bradford MA

Assignee:

American Telephone and Telegraph Company, AT&T Bell Laboratories - Murray Hill NJ

International Classification:

H04J 116

US Classification:

370 15

Abstract:

Method and apparatus for looping around a digital transmission line (150) at a predetermined channel unit (172) to test the line from either end of the line. Each channel unit in the line is responsive to a first and a second received control code to perform one of two operations. When the first and second received control codes are both first predetermined control codes from one end of the line, the data channel assumes a state to pass the second received first control code and any subsequently received control codes to the next channel unit. However, when the first and second received control codes are first and second predetermined control codes from the one end of the line, respectively, the data channel unit connects the transmit path from the one line end to the receive path back to the one line end, thus looping back to the digital transmission line. To loop around a line at a predetermined channel unit, a maintenance circuit (152) at one line end applies an individual first predetermined control code for the predetermined channel unit and each of the intermediate channel units followed by the application of a second predetermined control code for the predetermined channel unit. The first channel unit from the end of the line passes the second received first control code and any subsequently received control codes to the next channel.

US Patent:

46758623, Jun 23, 1987

Filed:

Nov 27, 1984

Appl. No.:

6/675123

Inventors:

Frederick J. Banzi - Andover MA
Michael J. Dugan - Merrimac MA
Craig A. Sharper - Bradford MA

Assignee:

American Telephone and Telegraph Company - Murray Hill NJ

International Classification:

H04T 116
H04B 346

US Classification:

370 15

Abstract:

A channel unit (172) for looping around a digital transmission line (150) in response to first and second received control codes. When the first and second received control codes are both first predetermined control codes from one end of the line, the data channel assumes a state to pass the second received first control code and any subsequently received control codes to the next channel unit. However, when the first and second received control codes are first and second predetermined control codes from the one end of the line, respectively, the data channel unit connects the transmit path from the one line end to the receive path back to the one line end, thus looping back the digital transmission line. To loop around a line at a predetermined channel unit, a maintenance circuit (152) at one line end applies an individual first predetermined control code for the predetermined channel unit and each of the intermediate channel units followed by the application of a second predetermined control code for the predetermined channel unit. The first channel unit from the end of the line passes the second received first control code and any subsequently received control codes to the next channel.