Nokia 2220 Servicehandbuch
CCS Technical Documentation
System Module
RH-42
Issue 2 09/2003
Nokia Corporation Confidential
Page 17
Lights
Introduction
RH-42 has has blue LEDs for lighting purposes. The LED type is blue-light emitting and
SMD through-hole mounted.
SMD through-hole mounted.
Interfaces
The display lights are controlled by a Dlight signal from the UEM. The Dlight output is the
PWM signal, which is used to control the average current going through the LEDs. When
the battery voltage changes, the new PWM value is written onto the PWM register. In
this way, the brightness of the lights remains the same with all battery voltages within
range. The frequency of the signal is fixed at 128 Hz.
PWM signal, which is used to control the average current going through the LEDs. When
the battery voltage changes, the new PWM value is written onto the PWM register. In
this way, the brightness of the lights remains the same with all battery voltages within
range. The frequency of the signal is fixed at 128 Hz.
The keyboard lights are controlled by the Klight signal from the UEM. The Klight output is
also a PWM signal and is used in the same way as Dlight.
also a PWM signal and is used in the same way as Dlight.
Technical Information
Each LED requires a hole in the PWB, in which the body of the LED locates in hole and
terminals are soldered on the component side of the module PWB. The LEDs have a white
plastic body around the diode, and this directs the emitted light better to the UI side. The
current for the LCD and keyboard lights is limited by the resistor between the Vbatt and
LEDs.
terminals are soldered on the component side of the module PWB. The LEDs have a white
plastic body around the diode, and this directs the emitted light better to the UI side. The
current for the LCD and keyboard lights is limited by the resistor between the Vbatt and
LEDs.
Audio HW
Earpiece
Introduction
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.
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.
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.
Buzzer
Introduction
The operating principle of the buzzer is magnetic. The diaphragm of the buzzer is made