Private Preview Setup
Scanning with private preview makes use of an earpiece for the private announcement of a button and an external speaker to sound the speaking message. You'll need a splitter cable or adapter to connect an earpiece and an external speaker to your iPad.
Please note, that you can't use the iPad's speaker with private preview. When you plug something in to the headphone jack on your iPad, the iPad's speaker is disabled and cannot be used.
Bluetooth speakers don't work with private preview. While you can place the Bluetooth speaker anywhere for the speaking message you can't use an earphone with it. If you plugged the earphone in to the Bluetooth speaker (if it had a jack) it would disable the speaker. If you plugged the earphone in to the iPad, the Bluetooth speaker is disabled.
The easiest way to do this is to use a stereo to mono Y cable with an adapter to make an easy connection with most iPhone/iPad-type external speakers. Here's an example from Guitar Center/Radio Shack:
For the earpiece you can use the earbuds from your iPad but it would be better to get a mono earphone such as these from Amazon. Here's a few examples: http://tapspeak.com/images/Choice40PrivatePreview/
There are probably hundreds of speakers you could get for the external speaker. You'll need to make sure the speaker is powered by batteries or rechargable batteries. It's best to get a mono speaker, one that has only one speaker in it. Here's a couple of examples
Finally, set up the scan settings to direct audio to the earphone and speaker. First, set up your buttons so that recordings are used for both the spoken message and the scanning message. We're not able to use text-to-speech voices at this time since there are no iPhone text to speech vendors that supply a stero voice.
Here's an example of what the scan settings screen should look like. After you set up your cable/earphone/speaker and your settings and the preview message comes out the speaker and the spoken message out the earphpone, either swap the panning in the settings or swap the earphone and speaker plugs on the adapter cable.