Section 45(b) in The Border Security Force (Ceremonials And Marks Of Respect) Rules, 1989
(b)The method of signalling words of command and the exact procedure to be adopted on each signal. Loud speakers are the best means, but they must be reliable and be suitably sited. An alternative method, e.g. , visual signalling must be laid down to be used in the event of loud speaker breaking down or the words of command not reaching the troops and the audience particularly those in the rear.
