The ‘S’ button on the AXIWI devices can be used to set the ‘speaking function ‘on’ or ‘off’. To enable or disable the speak function you push about 1-2 seconds on the ‘S’ button. At various sports it is desirable that some users only can listen (think of a 4th official) and the microphone is not permanently open. If this person wants to talk or want to participate in the conversation, then he can use the large PTT button (AXIWI OT-015) that fits good in the hand. With this PTT-button it is more practical, faster and easier to set the speaking function ‘on’ or ‘off”, than using the ‘S’ button on the AXIWI.