genuine lightning metal referee whistle stainless steel 201 copper whistle for sports basketball and football matches

Symbol Explanation: ● Short sound (within one second); ■■■ Long sound (over 3 seconds); The whistle sound within the instruction is 2-3 seconds, and the interval between instructions is over 30 seconds (e.g., to repeat the instruction, you need to wait over 30 seconds).
Communication (T): ■■■ (a long sound)
For team voice communication to determine the direction of each other's whistle signals, after receiving a whistle command, to respond with a call sign (similar to: "Hey~~~~~", reply: "Hey~~~~~").
Set (U): ● ● ■■■ (two short and one long)
Assemble toward the direction of the whistle (similar to the shout: 'Assemble!' used at the end of a football match)
Advance (V): ● ■■■ (one short and one long)
Rest time: the team's departure is signaled by a shout (similar to "Go!" or "Charge!").
Front of the line waiting (W): ● ■■■ ■■■
When the distance of the march is too long, the front team is required to wait for the rear team (similar to the shout: Please wait~~~ wait~~~)
SOS：● ● ● （三短）
When encountering difficulties and needing help, send out a signal. The receiver responds with a communication tone (T) ■■■ (a long sound) to indicate that they will be coming to assist (similar to a call for help: Hurry! Hurry! Hurry! Answer: Ahhh~~~).
SOS: ● ● ● ■■■ ■■■ ■■■ ● ● ● （三短 三长 三短）
This is the internationally recognized SOS code, please remember it well. (Can be translated as: Urgent! Urgent! Urgent! Help~~~ Life~~~ Ah~~~ Urgent! Urgent! Urgent!)

Packing quantity: 40 boxes/piece, 10 pieces/box

The rope length is about 45cm.

Material: Stainless Steel

Packing: Each whistle is packaged in a small box.