Lights; Introduction; Interfaces; Technical Information - Nokia RH-41 Series Technical Documentation Manual

CCS Technical Documentation

Lights

Introduction

RH-41 has blue LEDs for lighting purposes. The LED type is blue-light emitting and 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.
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.

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.

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.

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.

Buzzer

Introduction
The operating principle of the buzzer is magnetic. The diaphragm of the buzzer is made
Issue 2 09/2003
Nokia Corporation
Confidential
RH-41
System Module
Page 17