04039751 is referenced by 14 patents and cites 15 patents.

A method and apparatus are disclosed for closed loop testing of first and second modulators and demodulators from the modulated signal side of the first modulator and first demodulator. During ordinary communication, the first modulator and second demodulator are connected in series and the first demodulator and the second modulator are connected in series. In response to each test initiate signal, a loop is established between the second modulator and the second demodulator on their modulated signal side. Upon reception of some test initiate signals, a loop is established between the first modulator and first demodulator on their demodulated side and they are disconnected from the second demodulator and second modulator. Thus, the first modulator and demodulator can be tested from their modulated signal side when a loop is established between them; and the first and second modulators and demodulators can be tested when a loop is established between the second modulator and demodulator but not between the first modulator and demodulator.

Title
Method and apparatus for closed loop testing of first and second modulators and demodulators
Application Number
246589
Publication Number
4039751
Application Date
March 22, 1976
Publication Date
August 2, 1977
Inventor
G Howard Robbins
New Canaan
CT, US
Steven J Davis
Ridgefield
CT, US
Robert A Couturier
Stamford
CT, US
Agent
Pennie & Edmonds
Assignee
General Datacomm
CT, US
IPC
H04B 3/46
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