4.5.3 FREQUENCY SELECTOR
This control
operates as
in the Normal
Mode to
select
the
frequency
to be calibrated. All frequencies must be
calibrated
and they can be calibrated in any sequence.
4.5.4
PRESENT BAR
The
Present Bar controls the presentation of the
stimulus.
It
operates in
a push ON/push OFF manner.
If the Present
Bar is
operated
while the stimulus is off, the stimulus will be
turned
on and remain on until the Present Bar is operated a second time.
The
stimulus will actually be turned ON or OFF when the
Present
Bar is pressed.
4.5.5
HL DIAL
1.
This control performs the dual function of selecting the HL
level at which the calibration is being performed and of
adjusting the output level of the transducer.
2.
While the stimulus is off,
the HL selector will select the
Calibration HL level (Cal HL).
The level will be adjusted
up by 5
dB
for each clockwise step of the selector and down
by 5
dB
for each counter clockwise step.
For each change in
the Calibration HL level the transducer output level
(attenuator position) will be recalculated using the current
calibration data stored in the EEPROM.
The allowable range
of
the calibration HL will be from the nonextended
(+10
dB
range) maximum HL limit to 20
dB
below the limit.
Operation
of
the selector to select levels outside of this range
are
invalid.
When this occurs the level will default to the
limit and the HL display will be flashed.
3.
While the stimulus is on,the HL selector (dial) will adjust
the transducer output level to allow the SPL level to be
adjusted to the required SPL level on the sound level meter.
The output level will be adjusted up by 0.5
dB
for each
clockwise step of the selector and down by 0.5
dB
for each
counter clockwise step. The output level is changed
according to the HL selector by directly setting the
attenuator position. Operation of the HL dial to select
positions outside of the instrument range will be invalid.
The attenuator position will be adjusted within the limits
and the displayed SPL value on the HL display will be
flashed.
4.5.6 EXTENDED RANGE PUSHBUTTON
This pushbutton is used to store the transducer SPL
calibration
data
into
EEPROM.
After the calibration data is
successfully
stored,
the
EEPROM checksum will be updated
and
the
Patient
Response LED will be turned on for 2 seconds.
If the calibration
data can
not be stored successfully, the word
"CAL"
"
will be
flashed on the HL display and the previously displayed SPL value
22
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