White’s Electronics TDI SL 7.5 and 12 - Manual (Page 9)

Page 9
TDI SL
Owner’s Manual
Controls
Threshold
The
Threshold
control sets the level
at which the background audio tone is
heard. In most cases, faint target sig-
nals are easiest to hear when the thresh-
old is set to a low but clearly audible
level. A higher threshold level can
result in audio fatigue. Too low of a
threshold level means that a stronger
target signal is required to produce an audible change.
Thresh-
old
is best determined at a low gain setting where there is no
chatter.
The threshold can be set low enough to effect a “silent
search” audio. Some people prefer silent search to prevent
audio fatigue. If you choose to do this, increase the threshold to
the point where you can hear the threshold tone, then slowly
back off until it is barely inaudible. Reducing the threshold any
more than necessary requires stronger target signals to produce
an audio response. Other controls — including
Gain
,
Ground
Balance , and Frequency offset — are best adjusted with an
audible threshold.
Power/Gain
The
Gain
control increases or
decreases the amplification of the
receive signal. Normally, this deter-
mines how deep the detector will “see”
a target.
However, increasing the gain not
only increases the amplification of tar-
get signals, but also that of ground signals and electromagnetic
interference (EMI) as well. A common mistake is to assume