TM9100 Service Manual TOPA-SV-024 Test Unit 479
© Tait Electronics Limited August 2005
24.2 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.
24.2.1 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 receive 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.
24.2.2 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.
24.2.3 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 12kΩ resistor (R3) in or out of the MIC_PTT line.
■ When set to Off Hook, the 12kΩ 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 12kΩ resistor (R3) is switched into the
MIC_PTT line. This simulates the microphone being placed on the
microphone clip.
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