4.1 Signal Devices - Each rink must be provided with a siren, or other suitable sound devicethat will sound automatically at the conclusion of each period of play. Should the sound device fail to sound automatically when time expires, the determining factor as to whether or not the period has ended shall be the timing device.
Behind each goal, electrical lights shall be set up for the use of the Goal Judges. A red light will signify the scoring of a goal and a green light will signify the end of a period or a game.
A goal cannot be scored when a green light is showing.
A light, normally red in color, will be situated at or near the Timekeeper’s Bench and will be illuminated when a commercial time-out is in progress. This light will be extinguished when the commercial time-out is complete to indicate to the teams and the officials that play may resume. This light is controlled by an authorized National Hockey League Commercial Coordinator.
4.2 Timing Devices - Each rink shall be provided with some form of electronicclock for the purpose of keeping the spectators, players and game officials accurately informed as to all time elements at all stages of the game including the time remaining to be played in any period and the time remaining to be served by at least five penalized players on each Team.
Time recording for both game time and penalty time shall show time remaining to be played or served.
The game time clock shall measure the time remaining in tenths of a second during the last minute
s of each period.