Bosch TR-825

On/Off & Volume Control Turns the beltpack power on and controls head set volume.
Audio Channel Select Button Allows user to select either audio channel A or B.
Bat/Overmod Light (BAT/OM) Light will flash once when unit is turned on if the battery is good. If the light stays on, battery is low. If the light does not flash, battery is dead. A normal microphone gain setting will cause the LED to flash at the beginning of most words at normal speech levels. If the gain is too high, the LED will be red during the complete word at normal speech levels.
Talk Light LED is on when the talk button, SA or WTA is active.
Talk Button Press to enable the audio path from the local headset microphone. A quick press and release latches the talk function, unless latching has been disabled. Holding the button for over ½ a second will cause the audio path to be enabled only for as long as the button is held. If the talk function is latched on, pressing the talk button again will turn it off.