Bose T5 Service Manual page 23

PASS/FAIL Criteria. The level of sound
heard through the talk-through must not
in-crease dramatically after the sound of
the words stabilizes. If verification is needed
compare ambient sound at increased gain
level to sound heard through the talk-
through system. If headset's compressor
takes longer than 5 words to stabilize, it is a
failure.
6. Talk-Through Operation, ANR OFF,
Quiet Environment
This test is used to verify Talk-through
balance, intelligibility, and compressor
operation.
Set-Up Conditions.
•
TT switch - Talk-through ON - 0dB
•
Power supply input...3.0 Volts
(2 AA Batteries) in Control Module
• Headset Microphone switch - Off
• Headset Battery ANR Switch - Off
•
Sound Booth Noise Switch - Off
•
Sound Booth Audio Switch - On
6.1 Talk-through (TT) Gain. Listen to the
Talkthrough background noise in a quiet
environment. Exercise the TT Switch to
+5dB and +10dB positions respectively.
PASS/FAIL Criteria. The noise of the TT
circuit should increase for both earcups at
the +5dB position, and then increase for
both earcups again at the +10dB position.
The headset should not oscillate with either
+5 or +10dB gain.
Field Repair Light-up-and-Play Tests
1. Intercomm/Radio Communications Test
After repair, connect the headset to a
compatible radio or intercomm system and
verify that all functions work properly. Once
the headset has passed test, it can be
returned to use.
1.1 Connect the headset control module
cable to the radio or intercomm.
TEST PROCEDURES
23
1.2 Play an audio signal to the headset.
Verify that you can hear the audio being fed
to the headset from the radio or intercomm.
1.3 Speak into the microphone. Verify that
your voice signal is being received by the
radio / intercomm.
1.4 Disconnect the headset from the radio
or intercomm and perform the battery
powered tests located after the below noise
definitions.
Definitions
Background Noises Noise present in the
absence of other excitation, including the
following:
• Hum Constant low frequency signal,
caused by power line interference.
• Hiss Steady, broad mid-to-high frequency
signal caused by noise of headset electron-
ics.
• Static Intermittent crackling signal, caused
by external electrical interference.
• Whine Sharp continuous signal, caused by
narrow overvoltage pulses on power line.
• Ripple Noises caused by interference on
power supply line at various frequencies.
Instability Noises related to acoustic leaks
or malfunctions compromising stability,
including the following:
• Squeal Mid-to-high frequency variable
tone.
• Motor-boating Lower frequency periodic
noise.
• Buzz Harmonic produced by vibration in
the presence of an audio signal. This noise
is usually related to mechanical faults.
Overload Noises related to movement,
pressure or impact on headset as well as
extremely high external noise, including the
following:
• Click Sharp transient caused by collapse
of driver diaphragm. Generally very notice-
able.
• Thump Low frequency transient, caused
by saturation of headset electronics.
• Pop Low frequency transient, caused by
saturation of ANR loop.