Grounded analog section.
(a) The frequency modulated signal from opto-coupler K6 is
demodulated by a phase locked loop (PPL) and filtered to diagnostic frequency response
by a three pole 100Hz low pass filter. Similarly, the paddle preamplifier output signal from
the defibrillator section is filtered by a 30Hz low pass filter. When the 1mv calibration
button is depressed, both signals, plus an equivalent 1mv signal, appear at the inputs of a
group of analog gates. This automatically permits the selected signal to progress to the
size or manual gain control. From there, it goes to an internally selectable 50Hz or 60Hz
notch filter which also can be switched out of the circuit completely by another pcb
(b) The output signal of 1v per mv input is derived from the filters output
and drives the chart recorder when its diagnostic mode of operation is selected.
(c) The main amplified signal passes through a monitor quality filter with
a response of 0.5Hz to 40Hz and drives the digital circuits.
(d) The QRS filter and recognizer converts it into a 60msec pulse upon
recognition. This pulse activates the beeper through its volume control and continues to
the synchronizer logic. The synchronizer logic is enabled from the corresponding control
at the defibrillator. It provides the signal for the heart rate meter with the associated Hi and
Lo presettable alarms together with an independent asystole alarm.
(e) When any of the alarms is triggered and when the defibrillator is fired,
a timer runs the chart recorder for 15 seconds showing the information present in memory
from approximately six seconds before the actual alarm condition is detected. This mode
of operation requires that the chart recorder mode selector is in the AUTO position. The
other positions permit the selection of diagnostic or delayed signal recording continuously.
Monitor power supply.
(a) The primary energy for the monitor can be line power 50Hz or 60Hz
with selectable voltages of 120v or 240v, or from a self contained 2.2 ampere hour (AH)
NiCad battery. Switching over to line power occurs automatically as soon as the line cord
is plugged into an outlet, and the battery is recharged.
(b) If the monitor is turned on under line power conditions, a preregulator
circuit takes the place of the battery supplying approximately 12v to the main switching
power supply. This circuit delivers all the stabilized voltages for every stage in the monitor
and obtains its regulation through a Pulse Width Modulation (PWM) technique.
(c) When the battery voltage falls below 9.5v, an automatic shut off
feature shuts the monitor down completely. This stage also performs the local function
Monitor-ON-OFF and follows the command from System ON-OFF located on the