Philips M3921A, Service Manual

Page: 133 / 150

Theory of Operation and System Architecture
Chapter 10 - Training Program 121
System Overview - A3
The A3 is a full function monitor for use on adult and pediatric patients.
The functions performed by the system include monitoring patient ECG, heart
rate, respiration rate, blood pressures, blood oxygen saturation, and
temperature.
In addition to monitoring and displaying the status of these physiological
parameters, the instrument performs various microprocessor-programmed
analytical functions, such as:
• Creating both visual and audible alarm signals when set limits are
violated
• Creating and displaying warning messages when conditions are detected
that would degrade or prevent valid measurements
• Creating and displaying trend waveforms or tabular data;
• Providing a synchronizing pulse for defibrillator operation;
• Providing input to an optional recorder for printout of current or trend
waveforms or tabular data.
The monitor is essentially a battery-powered instrument. An internal charging
unit is designed to accept either an AC line voltage or DC source input
voltage. The charger uses these external power sources to maintain a “float”
voltage source available from the batteries.
Block Diagram - A3
The A3 functions are represented graphically in the System Block Diagram,
Figure 2.
Each section of the System Block Diagram is described briefly in the text that
follows the illustration. This is followed by more detailed descriptions of the
theory of operation of each block.