White’s Electronics TM 808 - Manual (Page 12)

3) Set the AUTOMATIC THRESHOLD control to the NO-AUTO posi-
tion. Note: Stay away from all metallic objects . . . . .cars, pipe, concrete re-bar,
etc. Remove all significant metal from your body. . . . .belt buckles, car keys,
watches, knives, etc.
4) Hold the instrument at arms length at your side as if you were hold-
ing a suitcase (approximately 18 inches above the ground), press the PUSH
BUTTON on the handle, hold for a second and release. The threshold tone
will be heard. Raise the instrument approximately six inches further above the
ground. If the THRESHOLD hum changes little or not at all, the initial GROUND
REJECT control setting "NORMAL" is adequate for searching in that particular
area. Switch the AUTOMATIC THRESHOLD control to the AUTO positions and
proceed to search.
5) However, if the THRESHOLD hum does change as the instrument is
lifted, leave the AUTOMATIC THRESHOLD control in the NO-AUTO position and
proceed to adjust to the ground in the following manner:
Tuning
1) Set the SIGNAL BALANCE, and GROUND BALANCE, to their NOR-
MAL positions. Set the AUTOMATIC THRESHOLD to the AUTO position.
2) Turn the THRESHOLD clockwise and check the meter to determine
conditions of battery pack (must be 75% or higher to operate the detector). The
THRESHOLD control, at this point, needs to be readjusted for a very faint hum.
The detector will operate well (locate metal) in most locations with the controls at
these settings. However, for optimum performance and penetration depth, fine
tuning of the GROUND BALANCE and SIGNAL BALANCE controls are neces-
sary.
GROUND BALANCE PROCEDURE
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