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From: die@cpoint.UUCP (David I. Emery)
Newsgroups: comp.sys.next,sci.electronics
Subject: Re: Mouse cord nuisance from lap (was Re: Monitors: What Next?)
Keywords: induction, magnetic coupling, corrdless mouse
Message-ID: <1381@cpoint.UUCP>
Date: 20 Nov 88 05:33:00 GMT
References: <15572@agate.BERKELEY.EDU> <16891@shemp.CS.UCLA.EDU> <31811@bbn.COM> <1405@neoucom.UUCP> <1227@microsoft.UUCP>
Reply-To: die@cpoint.UUCP (David I. Emery)
Organization: Clearpoint Research Corp., Hopkinton Mass.
Lines: 37

In article <1227@microsoft.UUCP> michaelw@microsoft.UUCP (Michael Winser) writes:
>In article <1405@neoucom.UUCP> wtm@neoucom.UUCP (Bill Mayhew) writes:
>>I'd like to see a microwave or infrared operated mouse that used
>>doppler shift or some form of interferometry for sensing motion
>>over an arbitrary surface.  I suppose this could be done with an
>

>I do think getting rid of the rodent's tail would be very nice, it's
>always getting tangled up with my keyboard and monitors etc.


	A boring bit of hardware suggestion.  IR is subject to shadowing by 
the users hand and rf links in VHF or UHF or low microwave are expensive
(because of the need to handle strong nearby signals) and there are only limited
channels available anyway.  How about plain old induction with the 
mouse transmitting somewhere in the vlf or lf range on a narrow band
fsk'd carrier (say 180 khz +- 500 hz) to a simple loop antenna in the mousepad
(and nearby for those who want to use the mouse on any surface).  A more complex
but interference resistant modulation might be some form of direct sequence
spread spectrum similar to what has been tried experimentally to send data
on carrier current over power lines.

	Unfortunately this implies a battery powered mouse unless the
pickup antenna loop could also serve to create a lf ac magnetic field strong
enough to power the mouse.

	One advantage of this is that, at least with a mousepad mouse,
the coupling would be uniformly strong near the mousepad and weak to the 
mousepad on the system at the next desk.  RF linked systems and especially
optical systems might have real problems with multiple mice in an office
area or terminal room due to mutual interference.


-- 
	David I. Emery   Clearpoint Research Corp. 
	99 South Street, Hopkinton Ma. 01748  1-508-435-2000
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