b) Mass Locating. At any time when the operator is using the
902 receiver for line tracing, he may choose to activate
mass locating mode. In this mode, the receiver sounds a
continuous tone and indicates detection of a metallic
mass with a notable shift in the frequency of the audio
tone. The frequency heard will rise when a conductive
mass is detected, and lower when a strictly ferrous mass
is detected.
3. Two-Box Modes.
The transmitter and receiver may be configured together to
enable location of "unknown" lines, lines which have no
known point at which to energize them. One method of find-
ing unknown lines involves having two operators, each hold-
ing one of the locator boxes and moving together in the area
that a line is suspected to be found.
D. Operating Procedures:
1. Energizing a Line to be Traced.
The Model 902 is an "active" locator. This means that the
902 receiver is designed to detect lines that have been ener-
gized by the signal generated from the 902 transmitter.
Therefore, the operator must prepare to trace a specific line
by first energizing it. Following are the methods for energiz-
ing lines.
a) Inductive Energizing
Using this method, the operator can energize the desired
line without having to make any physical contact with it.
Placed correctly upon the ground or pavement below
which the line to be traced lies, the transmitter radiates its
radio-frequency signal to the line
(Fig. 4)
. Once effected
10
