Assemblies Descriptions B: Theory of Operation
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defibrillator/monitor is disabled. External paddles have a Patient Contact Indicator (PCI) located on the
Sternum paddle. The contact quality is indicated on the PCI using red, orange, and green LEDs. Once
proper contact has been made, the PCI illuminates a green LED.
Printer Assembly
The Printer Assembly provides hard copy output of text, waveforms, event data, etc. The printer module
receives print commands from the Processor PCA and drives the printhead and paper motor accordingly.
It senses when the paper is out, or the door is left open.
It transmits 3.3-V serial and logic communication signals and 7-V printhead power from the Processor
PCA to the Printer Assembly.
Printing
All printing of data is handled by the Processor PCA. Waveforms, graphics, numeric values, and messages
are all generated and formatted by the Processor PCA, using either data it has or data it receives from
other parts of the device. This data is then passed to the I/O PCA in serial digital messages, via a ribbon
cable, and then on to the printer assembly.
Contrast
The printing contrast is controlled automatically by the printer itself. The printer module senses
printhead supply voltage, temperature and impedance, and adjusts drive voltage to the printhead (and
thus contrast) based on these readings.
Paper Detection
The printer incorporates an optical sensor that detects when there is no paper left, or when the printer
door is open. The information is passed to the Processor PCA in serial digital messages via the I/O PCA
and the flex circuit, and the Processor PCA generates the appropriate screen message and tones to alert
the user.
Clock Backup Battery
The Clock Backup Battery (lithium-ion battery located on the Processor PCA) provides standby power
to maintain the system time and date during times when the main battery is either absent or discharged
and no external power is supplied.
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