You need to connect the operator microphone to the Left Operator Microphone jack. 

After this, select Microphone as input source in the top panel of the Speech measurement window. 

Now when the operator clicks Start and talks into the microphone, the client will hear the speech from microphone in the client transducer.  
 
Note: the correct transducer needs to be connected to the board and selected as the transducer for measurement. E.g. Connect TDH-39 and then select it from the list.  
 

The ear signs to the right are selection of ears – left, right, or both. Select the ear where you want the patient to hear your speech and adjust level in dB until the patient hears you. 

If you want to deliver speech via microphone for both ears, select the both ears sign and then turn on Dichotic mode. The sound will go into both ears. 

If the operator wants to hear the Talk Back sound from the client, you need to connect another microphone to the Talk Back microphone jack. Talk Back is on by default. 

You can play sound into one ear and masking will play into the opposite ear, into the same ear or into both ears, depending on what option you select in the drop down below masking. For this, select, for instance, Left ear and then enable Masking as shown on the picture. Then select the sound for masking and click Play.  
 
 

The Talk Settings panel on the right contains controls for the level of Talk Back (the client talks to the operator) and Talk Over (the operator talks to the client when there is sound from CD is played to the client and you want to give the patient an instruction via microphone. To turn it on, use the Talk Over button under the ear selection signs.