Lesson 3/Learning Event 8
Learning Event 8: DELAY EQUALIZER GROUP, OA-880/FTC (UE-5).
The delay equalizer shown in figure 7 is used to provide compensation
for envelope delay distortion in voice-frequency lines or telephone carrier
channels.
a. Each of the six equalizer modules, contain two delay sections for a
total of 12 delay sections. Each of the 12 equalizer sections are designed
to select a small portion of the received signal spectrum and to adjust that
portion to phase distortion requirements.. You as a circuit conditioner may
be required to adjust all 12 sections of the equalizer or you may only have
to adjust 1 or 2 sections to meet the phase distortion requirements. After
equalization has been completed, the equalizer is left on line and becomes
part of the line conditioning equipment.
It is not to be disturbed by
anyone except authorized personnel.
b. Each of the delay equalizer section has a delay and a gain control
that functions in conjunction with the low (LO), high (HI) and OUT function
switch. The first delay module has a SIGNAL GAIN control that adjusts the
overall signal level, where the GAIN control of each delay section only
adjusts the gain for that specific frequency spectrum. When the LO, HI, OUT
function switch of a delay section is placed in the OUT position, the VF
signal bypasses that delay section and is applied to the next delay section.
For example, the first delay section of the equalizer is the 600 Hz section.
When the function switch is in the OUT position the VF signal bypasses the
600 Hz section and is applied directly to the 800 Hz section (second
section). When the function switch is in the HI position, maximum delay is
introduced and when it is in the LO position a smaller amount of delay is
introduced to the VF signal. The 600 Hz delay control permits adjustment of
the amount of delay within the HI and LO ranges.
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