LINE SYSTEM CHARACTERISTICS
The simplest form of two-wire line is produced by using bare conductors suspended on insulators at the top of poles (Fig. 37.3). The wires must not be allowed to touch each other; this would provide a short circuit and would interrupt communications.
Fig. 37.3 Simple overhead two wire lines
Another type of two-wire line consists of conductors insulated from each other in a cable, which also has an outer cover of insulation (Fig. 37.4). This outer sheath used to be made of lead but various types of plastic are now commonly used, particularly PVC. The two insulated conductors in the cable are often twisted together ...
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