Theory of Operation and System Architecture

Navigation Wheel

RS-232 I/O

Defib Sync Pulse

Speaker

The Contrast button operates in conjunction with the navigation wheel to determine the apparent contrast setting in the display. Changing the contrast is a change in the viewing angle. Outputs of the button and wheel are connected to the processor.

Momentarily pressing the button sets the contrast to mid-range, factory-default value.

Momentarily pressing of the button, followed within 3 seconds by a rotation of the wheel are processed to vary the contrast of the display. When there has been no wheel rotation for 3 seconds, the contrast control function is terminated by the processor. The contrast control function is also terminated if the wheel is pressed any time within this 3 second interval.

Operation of the Volume button accomplishes similar functions for the volume of the heart rate audible tone as the display contrast control button does for the display. Pressing this button, enables the wheel to vary the tone volume.

This is a rotating, push-switch wheel. The associated wheel circuitry generates a pulse when pressed and generates a digitally encoded pair of quadrature signals whose relative magnitudes and polarities represent the angular position of the wheel. These outputs are connected to the processor where they are interpreted as required for the functions involved. Successive angular positions determine the direction of wheel rotation.

In addition to the functions performed when in conjunction with the keypad as described above, the wheel operates in conjunction with the display to select menus and lists of parameter variables.

This is a rear panel 9-pin connector providing interfaces with other computer systems or equipment. The driver for this "port" is a Universal Asynchronous Receive-Transmit (UART) integrated circuit that interfaces this port with the microprocessor. The baud rate for this serial transmission function is programmable from 1200 baud to 38.4 kilobaud.

Pin number 9 of the RS-232 connector is reserved for a Nurse Call signal. The nurse call signal reacts when a low, medium, or high level alarm is activated.

The rear panel connector for the Defib Sync Pulse is keyed so that the connection of a cable can be detected by the processor. When a connection is detected, the processor software initiates the generation by hardware of a TTL-compatible pulse capable of driving 1 TTL load over a three-meter cable with less than 200 pF capacitance.

The defib pulse is triggered by the detection of the R-wave in the QRS sequence of the ECG wave-form complex. The pulse signal is active for 100 ±10 ms.

The speaker is capable of providing 73 dBA of volume at a distance of one meter during alarm conditions. The processor drives the speaker in different patterns as specified for the different alarm priorities and conditions. Refer to the C3 Instructions for Use guide for descriptions of alarm responses.

11-8Training

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Philips 862478, 862474 manual Navigation Wheel RS-232 I/O Defib Sync Pulse Speaker
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862474, 862478 specifications

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