Mindray BC-2800 - Buzzer Control; Control of LCD Brightness

Hardware
Figure 1-11 Control of LCD brightness
The LCD brightness is controlled by pot RV1. Adjusting the RV1 can force the
VBL to change within 0.5~3V. The voltage change is fed into the inverter and
causes the change of the drive current and hence the change of the brightness.
Note that the smaller the voltage and the brighter the LCD.
1.9.2.5 Buzzer control
The buzzer is controlled by a DC signal (5V DC; current<40mA). The 5V supply
of the buzzer is isolated from the VDD and the control signal is received through
a photocoupler （TLP521-2）that is controlled by a current around 10mA.
Figure 1-12 Buzzer control
BC-2800 Auto Hematology Analyzer (V1.0) 1- 17