White’s Electronics TDI - Manual (Page 16)

6 PulseScan TDI Owner’s Guide
FREQUENCY -
What it does
This control makes small adjustments up or down to the transmitter pulse
frequency or rate. This is used to counteract any interference which might be
due to outside electromagnetic sources, such as radio stations, microwave, short
wave, electric fences, power lines, lightening, electrical storms, or other metal
detectors being used nearby. This interference is recognized by a warbling or
pulsing of the audio threshold in a repetitive way, and can mask target signals.
The Pulsescan TDI has a frequency range of 3.25 kHz to 3.37 kHz pulses per
second.
How to use it
Electrical interference is not exclusive to urban areas, where power line harmon-
ics, local radio transmissions, or microwave transmissions can raise havoc with
the audio threshold. Getting too close to other metal detectors being operated
will also cause this problem. A slight adjustment of the frequency control can
help make the audio more stable.