Which item is not part of a lightning arrester system?

A lightning arrester system is designed to protect electrical installations from lightning strikes by providing a safe path for the electric current to follow, thus preventing damage. The components of a lightning protection system typically include a lightning rod, down conductors, and grounding or earthen materials.

The lightning rod is installed at the highest point of a structure to intercept the lightning strike. The down conductor is a conductive path that carries the electric current from the lightning rod down to the earth. Earthen materials or grounding systems are utilized to dissipate the energy safely into the ground, reducing the risk of injury or damage.

The correct choice, which is not a part of a lightning arrester system, is a transmitter. A transmitter does not have a role in lightning protection systems; instead, it is associated with communication technologies, such as sending signals or data. This distinction clarifies why the other options, which are essential components of the lightning protection system, are not suitable answers in this context.