Welch Allyn SureSight Autorefractor - User Manual - Manual (Page 33)

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a Field strengths from fixed transmitters, such as base stations for radio (cellular/cordless) telephones and
land mobile radios, amateur radio, AM and FM radio broadcast and TV broadcast cannot be predicted
theoretically with accuracy. To assess the electromagnetic environment due to fixed RF transmitters, an
electromagnetic site survey should be considered. If the measured field strength in the location in which
the SureSight is used exceeds the applicable RF compliance level above, the SureSight should be observed
to verify normal operation. If abnormal performance is observed, additional measures may be necessary,
such as reorienting or relocating the SureSight.
b Over the frequency range 150 kHz to 80 MHz, field strengths should be less than 3 V/m.
Recommended Separation Distances Between Portable and
Mobile RF Communications Equipment and the SureSight Vision Screener
The SureSight is intended for use in an electromagnetic environment in which radiated RF
disturbances are controlled. The customer or user of the SureSight can help prevent
electromagnetic interference by maintaining a minimum distance between portable and mobile
RF communications equipment (transmitters) and the SureSight as recommended below,
according to the maximum output power of the communications equipment.
Separation Distance According to Frequency of Transmitter (m)
Rated Max.
Output Power of
Transmitter (W) 150 kHz to 80
MHz
d = (1.17)
80 MHz to 800
MHz
d = (1.17)
800 MHz to 2.5 GHz
d = (2.33)
0.01 0.117 0.117 0.233
0.1 0.37 0.37 0.74
1 1.17 1.17 2.33
10 3.70 3.70 7.37
100 11.70 11.70 23.30
For transmitters rated at a maximum output power not listed above, the recommended
separation distance d in meters (m) can be estimated using the equation applicable to the
frequency of the transmitter, where P is the maximum output power rating of the transmitter in
watts (W) according to the transmitter manufacturer.
NOTE 1 At 80 MHz and 800 MHz, the separation distance for the higher frequency range applies.
NOTE 2 These guidelines may not apply in all situations. Electromagnetic propagation is affected by
absorption and reflection from structures,
objects, and people.