Main PCB Functional Circuits Description

Main PCB Assembly (803715)

The Main PCB Assembly, illustrated in Figure 1-4, consists of three major circuits: the Preamp, the System Controller, and the Display/Recorder Interface. The Preamp circuitry converts the ECG from the patient cable to sampled ECG. The converted ECG signal is optically connected to the System microprocessor which performs the initial ECG signal processing. The System microprocessor is central to the System Controller circuitry. The System Controller provides the interface between the operator inputs and the instrument functions. The Display/Recorder Interface controls the CRT and recorder displays according to the information supplied by the System microprocessor. The three major circuits control the functions listed in Table 1-2. Each circuit is described in the following paragraphs.

Table 1—2 Main PCB Functional Circuits

Preamp
System Controller
Display/Recorder Interface

Isolated Power Supply

Front and Rear Panel Controls Interface

Display/Recorder Controller

Front-End Protection

Audio Alarms

System Clock

Lead Select

Charge Control

Address Decode

Optical Interface

I/O Protection

Display Gate Array

Instruction Decoding

 

Video RAM

Instrumentation Amplifier

 

Font EPROM

Filtering

 

Program EPROM

DC Restore

 

Program RAM

Echo

 

Recorder Power

 

 

Motor Speed Control

 

 

Printhead Control

 

 

Printhead Resistance Evaluation

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