User's Manual

GC864 Hardware User Guide
1vv0300874 Rev.0 – 2010-01-25
Reproduction forbidden without Telit Communications S.p.A. written authorization - All Rights Reserved. Page 51 of 64
The disk and diaphragm are attracted to the core by the magnetic field. When an
oscillating signal is moved through the coil, it produces a fluctuating magnetic field,
which vibrates the diaphragm at a frequency of the drive signal. Thus the sound is
produced relative to the frequency applied.
Diaphragm movement
11.8.1 Frequency Behavior
The frequency behavior represents the effectiveness of the reproduction of the
applied signals.
Because its performance is related to a square driving waveform (whose amplitude
varies from 0V to Vpp), if you modify the waveform (e.g. from square to sinus) the
frequency response will change.
11.8.2. Power Supply Influence
Applying a signal whose amplitude is different from that suggested by manufacturer,
the performance change following the rule:
if resonance frequency
f
o
increases, amplitude decreases.
Because of resonance frequency depends from acoustic design, lowering the
amplitude of the driving signal the response bandwidth tends to become narrow, and
vice versa.
Summarizing: Vpp  Æ
f
o
 Vpp  Æ f
o

The risk is that the
f
o
could easily fall outside of new bandwidth; consequently the
SPL could be much lower than the expected.
11.8.3. Warning
It is very important to respect the sense of the applied voltage: never apply to the “ - “
pin a voltage more positive than the “ + ” pin . If this happens, the diaphragm vibrates
in the opposite sense with a high probability to be expelled from its physical position,
damaging the device forever.