How shall telephone lines be installed?

The correct choice reflects that telephone lines should be carried on insulators opposite the trolley wire and high voltage cables to ensure safety and effective performance. This method helps to prevent interference from other electrical lines and minimizes the risk of electrical hazards, such as arcing, which can occur if telephone lines are too close to high voltage sources. By utilizing insulators, the telephone lines are isolated and protected, thereby maintaining the integrity of the communication lines while also adhering to safety regulations.

Other methods of installation, while potentially functional, may not offer the same level of safety and reliability. For example, burying lines underground can protect them from environmental factors but may not be practical or permissible in all areas, particularly where other infrastructure exists. Installing lines in wooden conduits can sometimes be used but is typically not the standard installation practice for telephone lines in relation to high voltage systems. Affixing lines directly to power poles can expose them to greater risks concerning electrical interference and safety, particularly when those poles are also supporting high voltage lines. Therefore, using insulators opposite high voltage cables is the most appropriate and standard method for safely installing telephone lines.