28 Specifications and Standards Compliance
Fetal parameters, especially ultrasound and ECG, are sensitive measurements involving small signals,
and the monitoring equipment contains very sensitive high gain front-end amplifiers. Immunity levels
for radiated RF electromagnetic fields and conducted disturbances induced by RF fields are subject to
technological limitations. To ensure that external electromagnetic fields do not cause erroneous
measurements, it is recommended to avoid the use of electrically radiating equipment in close
proximity to these measurements.
Reducing Electromagnetic Interference
The device should not be used adjacent to, or stacked with, other equipment unless otherwise
The product and associated accessories can be susceptible to interference from continuous, repetitive,
power line bursts, and other RF energy sources, even if the other equipment is compliant with
EN 60601-1-2 emission requirements. Examples of other sources of RF interference are other medical
electrical devices, cellular products, information technology equipment, and radio/television
When electromagnetic interference (EMI) is encountered, for example, if you can hear spurious noises
on the fetal monitor's loudspeaker, attempt to locate the source. Assess the following:
Is the interference due to misplaced or poorly applied transducers? If so, re-apply transducers
correctly according to directions in this book, or in the Instructions for Use accompanying the
Is the interference intermittent or constant?
Does the interference occur only in certain locations?
Does the interference occur only when in close proximity to certain medical electrical equipment?
Once the source is located, there are a number of things that can be done to mitigate the problem:
Eliminating the source. Turn off or move possible sources of EMI to reduce their strength.
Attenuating the coupling. If the coupling path is through the patient leads, the interference may be
reduced by moving and/or rearranging the leads. If the coupling is through the power cord,
connecting the system to a different circuit may help.
Adding external attenuators. If EMI becomes an unusually difficult problem, external devices such
as an isolation transformer or a transient suppressor may be of help. Your service provider can be
of help in determining the need for external devices.
Where it has been established that electromagnetic interference is affecting physiological parameter
measurement values, a physician, or a suitably qualified person authorized by a physician, should
determine if it will negatively impact patient diagnosis or treatment.