Page 56
D00073611 Siemens SD 270 Service Manual
With “Primary phones” displayed use the Hz > key to cycle
through the available options (DD45,THD39,TDH49,E-5A) until
the required earphone type is displayed
Press the OPTIONS key to save the selection
Before calibrating the primary headphone ensure the correct earphone
type is displayed at the right of the lower line (only shown if a secondary
headphone has been enabled). If necessary use the PHONES key to
switch between the primary and secondary earphone types and then
calibrate as described in Appendix 5 Section 2. To retain existing
calibration values for other transducers do
not
use the ‘+20dB’ key to set
all calibration levels to zero.
Unless all other transducers are being calibrated at the same time it is
recommended that the calibration date is not changed but left as the date
of the original calibration. This will keep the calibration of the alternative
primary headphone in step with the remainder of the transducers.
On completion, the calibration process should be verified. The table in
Appendix 5 Section 4 may be used for this purpose, and if necessary the
entire calibration process should be repeated.
2
Secondary Earphone Type
The secondary earphone type may be set to one of:
None
Interacoustics DD45
Telephonics TDH-49
Telephonics TDH-39
Eartone 5A (E-5A)
Note that the audiometer does
not
store calibration data for all of the
above earphone types. These are simply labels to aid the operator in
identification of the secondary earphone type in use.
THEREFORE - IF AN ALTERNATIVE EARPHONE
TYPE IS SELECTED IT IS ESSENTIAL THAT THE
ACTUAL HEADPHONE TO BE USED WITH THE
AUDIOMETER IS THEN CALIBRATED WITH IT.