When a headset is inserted in J650, the internal speaker and microphone is disabled. The user can now use the headset for handsfree conversation. BOOM_MIC_DET

informs U1000 whether a headset is inserted or not. The state of BOOM_MIC_DET is controlled by Q1551.

When the headset is inserted the biasing voltage for the AUX_MIC will no longer be present at the base of the NPN transistor Q1551. This will switch Q1551 off, thus,

allowing BOOM_MIC_DET to be pulled high. When the headset is not inserted, the AUX_MIC biasing voltage is present at the base of Q1551. This condition will

switch Q1551 on, thus, pulling the BOMM_MIC_DET to ground.

CR1071 and CR1070 are devices used for ESD protection for its corresponding line.

P8190: