User Guide

The display backlighting is sourced from the constant current regulator N2301 and enabled from the PWM

300 output from Betty. The current is set by the 33R resistor to ground.

Figure 63 Lighting areas

Figure 64 Display and key backlighting control

Ambient Light Sensor

In order to optimise user interface legibility, the display and UI illumination brightness is controlled by the

handset according to the ambient lighting conditions. The ambient light level is measured by the handset

using the Ambient Light Sensor/Detector N6502 which communicates to the engine via the I2C interface:

RM-348; RM-349; RM-350

System Module and User Interface

Page 8 –18 COMPANY CONFIDENTIAL Issue 2