What distance should 2-way communication facilities be from the mine portal?

The correct distance for 2-way communication facilities to be positioned from the mine portal is 500 feet. This requirement is crucial for ensuring the safety and effective communication of personnel within a mine. The distance is designed to minimize potential interference from the environmental conditions around mine portals, such as dust, noise, and other hazards, which could disrupt communication.

By maintaining a distance of 500 feet, the communication systems can function more reliably, ensuring that miners have access to vital information and can send emergency alerts if necessary. This guideline reflects the operational realities of mining environments, where clear lines of communication are essential for safety protocols and efficient operations.

Other distances, such as those proposed in the other options, do not provide adequate separation that could warrant consistent and reliable communication, which is why they are not considered appropriate distances for the installation of these critical facilities.