Tait TM8235, Service Manual

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TM8100/TM8200 Service Manual TOPA-SV-024 Test Unit 573
© Tait Electronics Limited June 2006
34.2 Operation
This section explains the function of the TOPA-SV-024 test unit controls.
The procedure for using the test unit is described in the relevant section on
test equipment setup.
34.2.1 Portable / Mobile Switch
This 2-way toggle switch is used to switch attenuation resistors (R4, R5, R6)
in and out of the line from the radio’s positive speaker output to the positive
Rx Audio/SINAD
output of the test unit (before the isolating transformer).
■
When set to
Portable
, the attenuation resistors are switched out.
■
When set to
Mobile
, the attenuation resistors are switched in
(attenuation 10:1).
Important
Selecting the wrong switch position may result in incorrect
SINAD readings and damage to the test unit.
34.2.2 Mod Audio/Audio Tap In / Off / Mic Audio Switch
This 3-way toggle switch is used to switch between
Mod Audio/Audio Tap
In
,
Mic Audio
, and
Off
(no audio signal).
■
With the Tait Orca portables, this switch can be used for setting up dual
point modulation by applying modulation to different parts of the radio.
■
For normal transmit deviation tests (other portables and mobiles), this
switch is set to
Mic Audio
.
34.2.3 On Hook / Off Hook Switch
Important
When using the test unit with portables, the
On Hook
/
Off Hook
toggle switch must be set to
Off Hook
.
Portables do not have a hookswitch, and if the switch is set
to
On Hook
, the accessory function key of the portable is
activated.
This 2-way toggle switch is used to simulate the microphone hookswitch
opening (“hook off ”) and closing (“hook on”). This is done by switching a
12k
Ω
resistor (R3) in or out of the MIC_PTT line.
■
When set to
Off Hook
, the 12k
Ω
resistor (R3) is switched out of the
MIC_PTT line. This simulates the microphone being removed from the
microphone clip.
■
When set to
On Hook
, a 12k
Ω
resistor (R3) is switched into the
MIC_PTT line. This simulates the microphone being placed on the
microphone clip.