JK Audio THAT-1 - Manual (Page 4)

4
Operation
The Handset / Line In button selects which signal will
be sent down the phone line; the handset microphone,
or the line input jack.
When the Handset / Line In button is out, you can use the
handset to speak and listen as you normally would. The
sound that you hear on the handset is always available on
the From Phone output jack.
With the button in, the handset microphone is disconnected
and the line input is connected to send audio signals down
the line.
You can also use the Handset / Line In button to turn off
the handset mic if you are listening to the line output signal
over a loudspeaker. This will prevent feedback between
the handset microphone and loudspeaker. In any case you
can always listen over the handset receiver.
If a conflict arises it will typically be on the line input side. If
you attempt to send voice band signals down the line input
jack and the distant party complains that the level is too
loud or severely distorted (clipping), try to lower the
transmit signal on your audio equipment. If this does not
help, discontinue use immediately.
Note: Not all telephones are built alike so we cannot guar-
antee THAT-1 will work with any handset design out
there. We designed the interface to work with most
popular designs.