White’s Electronics TDI SL 7.5 and 12 - Manual (Page 17)

Page 17
TDI SL
Owner’s Manual
A lower threshold makes the TDI quieter and less chattery
but also requires a stronger target signal to produce a tonal
response:
A lower threshold can be played off against a higher
Gain
set-
ting, although you may find that the net outcome is about the
same.
Setting the threshold exceptionally low can result in a
“silent search” audio, whereby there is no audio sound until a
target is detected:
The drawback is that sensitivity can be markedly reduced and
weaker targets completely eliminated. However,
Gain
can be
increased to counter this, though the net result is still likely to
be less sensitivity than an optimally adjusted threshold.
Pulse Delay
Sampling as close as possible to the end of the transmitted
pulse gives the highest sensitivity to all metal targets regardless
of their size or conductivity. As the
Pulse Delay
is increased
toward 25 s low-conductive targets will drop out, leaving only
the more high-conductive targets.
Conductivity is not the only factor that determines how tar-
gets respond; size, thickness, and shape also have a strong influ-