(c) The small but unavoidable leakage currents tend to discharge the
bank to a voltage so low that the preset energy would be undeliverable. In order to avoid
this, a refreshing cycle (governed by the high voltage regulator) turns the main invertor
briefly on, keeping the system ready indefinitely or until fired.
Safety dump, manual dump, and automatic dump.
(a) If the load impedance is higher than 100 ohms, the pulse would
extend too long in time, or in the case of open circuit firing, the bank would be connected
to the paddles indefinitely. To avoid this highly undesirable situation, a 35msec timer is
started each time the fire SCR enters conduction. At the end of its cycle it throws the
dumper SCR into conduction. This terminates the pulse regardless of the total energy
(b) The red push button on the panel covers the manual dump function
such that the charge cycle can be interrupted and the bank can be totally discharged at
any moment. A similar action takes place if, during charge up or ready condition, the
energy selector is set to a different position. Finally, if the charged up unit is turned off,
again a pulse triggers the dumper SCR only.
Hold OFF logic, type of paddle sensor.
(a) After firing, these circuits avoid automatic recharging and also sense
the no paddle condition and limits maximum delivered energy to 50 watt/seconds for the
(b) Any normal condition related to the paddles will generate an "ERR"
(error) signal on the selected energy display, and the unit will not charge up.
Fire and synchronizer logic.
(a) This circuit requires that both paddle fire buttons have to be
depressed simultaneously in order to fire the defibrillator with a regular paddle set. The
firing can be accomplished with the single fire button on the panel only if internal paddles
are used. If anterior/posterior paddles are used, the firing is possible using the single fire
button on the anterior paddle.
(b) When the sync button is depressed, a third signal is required for the
firing. This signal is delivered by the sync circuit in the monitor and derived from the QRS