Passport 2®/Passport 2 LT™ Service Manual 0070-10-0441 2 - 31
Theory of Operation Patient Connector Board H.P.
2.6 Patient Connector Board H.P.
The ECM Patient Connector board is intended for use with cables having integral 1k
resistors, which eliminate the possibility of harmful arc-over at the connector pins during
defibrillation.
2.6.1 Spark Gap Suppressor
The patient cable is attached to the patient connector board. The clamping of defibrillator
transients, consisting of a neon bulb with each electrode circuit which clamps the peak
voltage with respect to isolated ground in series with the coupling capacitors. The cable
resistors absorb the remaining defibrillator voltage.
2.6.2 Neon Bulbs
This board provides defibrillator overload protection in conjunction with the front-end board.
The neon bulbs have a breakdown voltage range 60 v to 75 Volts. The patient’s ECG and
Respiration signals pass through the neon bulbs, which suppresses the defibrillation pulses.
2.6.3 Low-Pass Filter
The patient cable is attached to the patient connector board. The ECG signal and the
respiration signal pass through the HP connector J1. This board contains 3 LC Low -Pass
Filters with a minimum roll-off frequency of 17 MHz. A cut-off frequency of 23 MHz
(-3dB).
2.6.4 EMI Suppressor
The temperature probe connects to a three-circuit phone jack connector on the Patient
Connector board. The temperature circuit provides high-precision measurements of the
thermistor resistance, while using a minimum of precise components. This module also
features electrosurgical interference suppression (ESIS) and EMI suppression. The Connector
cable is used to reduce Conducted Susceptibility and Radiated Susceptibility induced by the
high frequency fields. The module serves simply as a connector; the signals pass through
efficiently and with minimum loss.
2.6.5 Patient and Power Isolation
This power supply requires sufficient isolation between the input and output to withstand the
voltage of a defibrillator, up to 2.5 kVrms. Further, it requires low capacitance between the
input and output, to minimize leakage currents which may flow should the patient
accidentally contact line voltage. The patient’s signals in the Patient Connector board must be
isolated to the same degree as the power supply and the ground.
2.6.6 Provide Mating for ECG, Temperature and two IBP connectors
The patient cable is attached to the monitor at the Patient Connector board. From the
connector board, the signal flows to the Front-End module, where the bulk of the ECG
processing is performed the transducers are plugged into the monitor via the Patient
Connector board. The Connector board bridges the excitation and ground of the transducers
together, then passes the signals to the main board.
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