http://www.iwf.net/doc/technical.pdf
3.3 ELECTRONIC REFEREE LIGHT SYSTEM
3.3.1 ELEMENTS OF THE SYSTEM

3.3.2 OPERATION OF THE SYSTEM
3.3.2.1 During the course of the competition, as soon as the three (3) referees have judged a lift “Good lift”, they press the white button on their control box. Immediately, the apparatus located in front of the platform gives a simultaneous visual and audible “Down” signal indicating the competitor to replace the barbell on the platform. When the “Down” signal has been given and the "Decision lights” are on and the competitor does not lower the barbell, the centre referee must say “Down” and signal the athlete to lower the barbell.
3.3.2.2 When the three (3) referees judge that the athlete has committed a fault during the execution of a lift, they give a “No lift” decision by pressing the red button on their control box. Immediately, the apparatus in front of the platform gives a simultaneous visual and audible “Down” signal indicating the competitor to replace the barbell on the platform.
3.3.2.3 The visual and audible “Down” signal is given as soon as two of the referees have given identical decisions.
3.3.2.4 Should one of the referees press the white button and another press the red button while the third referee does not press any, the latter hears an
intermittent audible signal coming from the control box urging him to give
his/her decision. Also, when any two (2) white lights or two (2) red lights have been given by two (2) of the three (3) referees and the “Down” signal has been seen and heard, then the third referee is reminded to give his/her
decision by the intermittent audible signal.

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Note added at 2 days 15 mins (2018-03-24 12:51:47 GMT) Post-grading
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