104
Connecting Third-Party Products
TM8000 3DK Hardware Developer’s Kit
Application Manual
September 2003
© Tait Electronics Ltd
Choose values for C50 and R53 as follows:
1.
Measure the earphone DC resistance R
E
using a multimeter.
2.
Choose C50 to be at least 10 µF and R53 to be approximately equal
to R
E
.
3.
Select an on-air channel with frequent voice activity and disconnect
the internal speaker.
4.
Turn the volume to
minimum
and plug the headset into the
microphone socket.
5.
Select and test the value of R53 until the desired headset volume is
achieved when the radios volume control is turned up to maximum.
Ensure the radio is powered down when making changes to the value
of R53.
6.
Select the value of C50 to be 1/(1900 ·(R53 +R
E
))
7.
Round this result to the nearest preferred value.
The radios internal speaker should be left disconnected.
Figure 5.3
Positions of C50, R52 and R53 on the control-head board
bottom side