Re: McDonnel Douglas warns against carry-on electronic devices

From:         yarvin@CS.YALE.EDU (Norman Yarvin)
Organization: Yale Computer Science Department
Date:         18 Jan 93 08:20:22 PST
References:   1 2 3
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  or MIME structure (Dennis Chamberlin) writes:
>I guess I can't swallow the idea that a passenger's CD player is going to 
>find its way into nav or other avionics gear. If the manufacturer really 
>said this, I interpret it as straw-grasping in the absence of other 
>The most powerful components of a CD player are presumably the motor drive
>and audio output.

A CD player is a digital device.  Thus it generates the sort of RFI a
computer generates.  Digital devices have voltages which transition sharply,
generating relatively strong radio frequency pulses relative to analog
devices, where changes in voltage are much slower.

Computers often have some sort of shielding, whereas the average CD player
probably only has as much shielding as is necessary to protect the analog
components from the RFI emanated by the digital components.  This is just a
guess of mine, based on the thinking that CD players are cheap mass-market
devices whose generation of RFI is not generally perceived as a concern.

It seems to me that if any small non-radio appliance is plausible as a cause
of RFI, a CD player is.

Norman Yarvin