GE Dash 3000 Service Manual page 239

Real-Time Clock
Audio Subsystem
Video Subsystem
Analog Outputs
Revision A
Assembly Drawings: Theory Of Operation
The real-time clock incorporates an on-board quartz crystal. This feature
simplifies the design and eliminates adjustments. The time of day is
maintained to an accuracy of 15 seconds in 24 hours to support 24 hour
trend data. The RTC device is one of the devices on the I
Audio tones are generated using a tone generator, an audio amplifier,
and an 8Ω, 2.5-in. speaker. The tone generator has built in D/A
converters and a mixer to generate the dual frequency tones.
Frequencies ranging from 150 Hz to 2800 Hz are produced.
The microprocessor contains a video controller that supports real-time
and non-real-time waveform drawing, menu drawing, and parameter
display.
Display brightness is controlled by a 50 kΩ digital potentiometer. The
potentiometer is interfaced to the brightness control input of an inverter.
Two analog output channels support ECG and BP. The pace pulse is
generated on the main processor board and inserted into the analog out
ECG signal. The digital-to-analog conversion for both ECG and blood
pressure output signals are performed on the main processing board via
a two channel 12-bit serial DAC. Cal data is stored on the processor/
power management PCB.
Dash 3000/4000 Patient Monitor
2000966-339
2
C bus.
9-15