Loud Speakers Used on Aerial Ladders Something novel from the viewpoint of American fire practice. has been developed by an English company. It is a loud speaker unit to be placed on aerial ladders so that an officer on the ground will be able to give direction to men working at higher levels. It operates on a voltage which can be found in the electrical circuit of the fire apparatus. There is a connecting cable operated by a selfwinding drum. This ensures the cable being drawn in or out as the extension ladder is operated. There have been a number of devices placed on European markets to facilitate the officers giving orders to men who were located in a burning building or at some other high point.