What sound signal is used for requesting an opening for the First Avenue South Bridge?

The sound signal used for requesting an opening for the First Avenue South Bridge is a signal consisting of three short blasts of the horn, known as "3 PL." This particular signal indicates to bridge operators that a vessel intends to pass through and requests the bridge to open.

In marine communication, specific sound signals are standardized to convey distinct messages. The three short blasts are widely recognized in maritime practice as a request for an opening, ensuring that bridge operations maintain safety and efficiency for vessels navigating the waterway. Understanding these signals is crucial for compliance with navigational laws and effective communication between vessels and bridge operators, thereby promoting maritime safety.

The other sound signals listed—one short blast, two short blasts, and four short blasts—are designated for different purposes and do not indicate a request for an opening of the bridge. It is essential to be familiar with these classifications to facilitate smooth maritime operations and communication.