Nokia NKC-1X Series, Technical Documentation Manual

Page: 18 / 54

NKC-1X
System Module CCS Technical Documentation
Page 18
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Nokia Corporation Issue 1 02/03
Audio HW
Earpiece
Introduction
The Philips Speaker System 13mm speaker capsule is used in NKC-1X .
The speaker is a dynamic one. It is very sensitive and capable of producing relatively high
sound pressure also at low frequencies. The speaker capsule and the mechanics around it
together make the earpiece.
Microphone
Introduction
The microphone is an electret microphone with an omnidirectional polar pattern. It con-
sists of an electrically polarized membrane and a metal electrode which form a capacitor.
Air pressure changes (for example, sound) moves the membrane, which causes voltage
changes across the capacitor. Because the capacitance is typically 2 pF, a FET buffer is
needed inside the microphone capsule for the signal generated by the capacitor. Because
of the FET, the microphone needs a bias voltage.
The microphone manufacturers for the NKC-1X transceiver are Matsushita and Hosiden.
Buzzer
Introduction
The operating principle of the buzzer is magnetic. The diaphragm of the buzzer is made
of magnetic material and it is located in a magnetic field created by a permanent mag-
net. The winding is not attached to the diaphragm, as is the case with the speaker. The
winding is located in the magnetic circuit so that it can alter the magnetic field of the
permanent magnet, thus changing the magnetic force affecting the diaphragm. The
buzzer's useful frequency range is approximately from 2 kHz to 5kHz.
The Buzzer manufacturer for the NKC-1X transceiver is Star.