3692939 is referenced by 5 patents and cites 2 patents.

A data modem is provided with loop-back circuits between the modem transmitter and receiver. If the modem is operating, the loop-back circuits cause oscillations. In addition, the oscillations can also indicate the operating condition of the modem so that adjustments can be made if needed.

Title
Test arrangement for data modem
Application Number
05/130,929
Publication Number
3692939
Application Date
April 5, 1971
Publication Date
September 19, 1972
Inventor
Stapleton Raymond D
Knight Patrick E
Assignee
General Electric Company
IPC
H04m 11/00
H04L 01/24
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