b. Operation. Figure 67 is a schematic diagram of a simplex telephone circuit superimposed on a metallic
telephone circuit. Telephone sets T1 and T2 are connected to the metallic two-wire line by means of repeating coils RC1
and RC2, respectively. These two sets operate as a two-way full-metallic telephone system. By means of the repeating
coils, an additional telephone circuit, or branch, is provided. This branch consists of telephone sets T3 and T4, and one
terminal of each is connected to the center terminal on the secondary of its associated repeating coil. The other terminal is
connected to a good ground, to furnish the return path for the current in the branch. The additional circuit thus provided is
called a simplex circuit, and the metallic circuit on which it is superimposed is said to be simplexed by the ground-return
circuit.
FIGURE 66. Line Terminating and
Simplex Panel.
FIGURE 67. Simplex Telephone Circuit.
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