Many office phones and smartphones have mute buttons that enable users to mute the line. If it is not possible to mute a line from the phone's controls, many conference lines have touch-tone key codes that can mute individual lines or all lines during a conference.
Office phones and smartphones can often be silenced by pressing the mute button either on the phone keypad or the touch screen. For example, on an iPhone, after clicking the call button, several icons appear on the touch screen, including the mute button. After clicking the button, a line appears through it, showing that the line is muted.
Services such as Free Conference and Zip Conference allow users to use touch-tone code *6 to mute or unmute an individual line. In some cases, the moderator of the conference may be able to enter another code, such as *96, to mute all lines.