Talk-Through Level Adjustment - Tait TM8000 Service Manual

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4.2

Talk-through level adjustment

The talk-through or side-tone feature is enabled by fitting optional component
VR3 (Tait IPN 040-06000-00). This allows audio which enters the TA2922
interface on the balanced or un-balanced line in path to be re-routed back out on
the balanced or un-balanced line out path.
Situations where this would be used is to provide microphone-to-earpiece side
tone, or when a single input voice recorder system needs to record both transmit
and receive sides of a two-way conversation.
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TA2922 Universal Line Interface Service Manual
© Tait Electronics Limited March 2010
Set the radio communications analyser to monitor the radios RF
transmission.
Set the audio generator to produce a 1kHz audio tone at the desired level.
Activate the TX key input to the TA2922 interface to set the radio to
transmit.
Monitor the transmitter deviation using the communications analyser and
adjust RV2 on the TA2922 interface to achieve 60% system deviation
(1.5kHz for narrow band, 3kHz for wide band).
This feature cannot be used when the TA2922 is operating in 2-
wire mode. Fitting VR3 when in 2-wire mode may cause audio
oscillations or instability.
Fit VR3 to the TA2922 interface by soldering in the three component leads.
Align both the line in and line out audio levels as described in the previous
section.
Disable the RF output of the communications analyser so that the radio is
in an idle state (not transmitting and not receiving a RF signal).
On the communications analyser, generate a 1kHz tone at the nominal
audio level, connect this to the TA2922 line input.
Ensure there is a 600 ohm termination resistor fitted across the two balanced
line out audio wires.
While continuing to generate the 1kHz tone, monitor the TA2922 line
output on the communications analyser.
Adjust VR3 on the TA2922 line interface to set the desired talk through
audio level.
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