System for locally testing a modem employing frequency shift keying
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United States of America Patent
Stats
-
Jul 12, 1983
Grant Date -
N/A
app pub date -
Jun 23, 1981
filing date -
Jun 23, 1980
priority date (Note) -
Expired
status (Latency Note)
Importance
Abstract
A test system is used to test a modem whose modulator is constituted by a multivibrator which during normal operation produces two frequencies f.sub.1, f.sub.2 in response to the data signal and which is connected to a transmission filter. In response to a test control signal, the multivibrator is modified to supply two test frequencies f'.sub.1 =nf.sub.1, f'.sub.2 =nf.sub.2, n being substantially equal to the ratio F.sub.o /f.sub.o, F.sub.o being the average value of the frequencies received by the modem during normal operation, f.sub.o being the average value of the frequencies f.sub.1, f.sub.2 ; at the same time the transmission filter is modified to transmit the two frequencies f'.sub.1, f'.sub.2 in response to the test control signal.
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