Textron Greenlee 77M-G Manuel D'instructions page 7

Supplying Talk Power
Connect the test leads in series with a telephone test set
(buttset) and the inactive wire pair (Figure 2). Move the toggle
switch to the SHORT position to supply the "dead" line with talk
power.
Additional test sets may be added, in series (red clip to
black clip), to increase talk power supply when needed
(Figure 2).
Figure 2. Supplying Talk Power
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