well as an envelope-delay characteristic curve from readings obtained in the
two preceding tests. This provides him with a visual aid to guide him in
his work.
c. Correcting delay distortion.
(1) Adjust FREQUENCY KHZ controls so that the delay inserted by the
CN-1234A/GCC is greatest where the telephone line has the least delay. The
initial settings depend upon the maximum delay time determined by analysis
of the delay characteristic curve.
The settings are afterward varied,
depending on the particular telephone line characteristics.
(a) When maximum initial delay is 3 ms or less, the FREQUENCY KHZ
controls are adjusted to one set of values.
(b) When maximum initial delay is between 4 and 7 ms, these
controls are adjusted to a different set of values. A line having greater
than 7 ms delays should not be used for data.
(c) When maximum initial delay is
between 3 and 4 ms, these
controls are varied slightly to establish
the best set of operating
conditions.
(d) Recommended FREQUENCY KHZ control setting are given below.
(2) Using the receiving TS-2669/GCM to monitor delay, increase
the
amount of delay in the equalizer at the midband frequencies to equal
the
delay at the ends of the frequency band. Remember that the basic intent
for
delay equalization is not to eliminate delay, but rather to minimize
the
variation in delay across the band of interest.
(3) Keeping the modulation rate constant,
adjust
the
TS-2669/GCM
carrier frequency to match the FREQUENCY KHZ
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