Philips HeartStart XL - Defibrillation Functions; Charging; Delivering a shock

M4735A Service Manual 6-9
System Functional Descriptions
6
Defibrillation Functions
The following sections describe the defibrillation functions.
Charging
There are three basic events that can initiate a charging cycle:
z In AED Mode, when the analysis algorithm determines a shock is
needed and sends a signal to another section of the Control PCA.
z In Manual Mode with either pads or paddles, when front panel key #2
(CHARGE) is pressed, the keypress is transferred from the key to the
Keyscan PCA via a flex circuit. The Keyscan PCA transfers the
keypress to the Control PCA via a large ribbon cable. The keypress is
then detected and processed by the Control PCA.
z Also in Manual Mode when the Apex paddle CHARGE key is pressed,
the keypress is transferred from the key to the Power PCA via the
paddles cable. The Power PCA transfers the keypress to the Control
PCA via a large ribbon cable. The keypress is then detected and
processed by the Control PCA
In all cases, the charging cycle is initiated and controlled by the Control PCA.
It directs the Power PCA to begin charging the charge capacitor, and it
monitors the voltage on the capacitor as reported back by the Power PCA.
When the Control PCA detects that the selected energy (voltage) level has
been reached, it directs the Power PCA to stop charging. The Control PCA
then continues to monitor the voltage on the capacitor, and as the voltage
bleeds down it directs the Power PCA to top up the charge to the correct level.
Should a decision be made to change the selected energy to a lower value, the
user would turn the Energy Select Switch to the desired setting. At the lower
energy setting, the Control PCA directs the Power PCA to disarm (completely
discharge) the capacitor then charge up to the new (lower) level.
If the requested charge is not used within 30 seconds, the Control PCA
automatically directs the Power PCA to disarm the capacitor as a safety
precaution.
Delivering a shock
The discharging cycle (delivering a shock) is initiated by either of two events.
z The first is by pressing the front panel key #3 (SHOCK) when using
pads. This keypress is transferred from the key to the Keyscan PCA
via a flex circuit. The Keyscan PCA transfers the keypress to the Con-
trol PCA via a large ribbon cable. The keypress is then detected and
processed by the Control PCA.