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'[OT] Old TV remotes that used ultrasonic?'
1997\10\07@120607 by Eric Thompson

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I was looking for some information on how the old TV remotes worked that
used ultrasonics for the remote controls.

I have an old TV that I lost the remote for (during a move) and would
like to create an Infrared to Ultrasonic converter (using a PIC of
course!) so that I can use my All for One IR remote with this TV.  Does
any one know how these remotes worked?  The remote only had 4 functions:
Chan. Up and down, and Volume up and down, so I'm assuming it uses a few
different frequencies to trigger these four functions.

As far as using a PIC for this, I have done the IR receiving part before
so that's not a problem, it's the ultrasonic part that I don't know
about.

So my questions are:
1) What sort of method was used to communicate from the remote to TV
with ultrasonics?

2) How would I create an ultrasonic sound using a PIC?


Thanks,
       Eric Thompson

1997\10\07@121854 by John Shreffler

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part 0 1089 bytes
-----Original Message-----
From:   Eric Thompson [SMTP:spam_OUTEricThompsonTakeThisOuTspamVERSALOGIC.COM]
Sent:   Tuesday, October 07, 1997 11:57 AM
To:     .....PICLISTKILLspamspam@spam@MITVMA.MIT.EDU
Subject:        [OT] Old TV remotes that used ultrasonic?

I was looking for some information on how the old TV remotes worked that
used ultrasonics for the remote controls.

I have an old TV that I lost the remote for (during a move) and would
like to create an Infrared to Ultrasonic converter (using a PIC of
course!) so that I can use my All for One IR remote with this TV.  Does
any one know how these remotes worked?  The remote only had 4 functions:
Chan. Up and down, and Volume up and down, so I'm assuming it uses a few
different frequencies to trigger these four functions.

As far as using a PIC for this, I have done the IR receiving part before
so that's not a problem, it's the ultrasonic part that I don't know
about.

So my questions are:
1) What sort of method was used to communicate from the remote to TV
with ultrasonics?

2) How would I create an ultrasonic sound using a PIC?


Thanks,
       Eric Thompson

1997\10\07@124404 by Steve Smith

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>I was looking for some information on how the old TV remotes worked that
>used ultrasonics for the remote controls.

Try rattling a bunch of keys this often opperates these aincent tv's .I bin'd
mine over 15 years ago.

Cheers Steve.....

1997\10\07@130248 by Miller, Steve

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Most of these remotes operated by a little hammer striking a metal rod whose
length is tuned to the ultrasonic frequency required.  Try this experiment.  Get
a small loudspeaker, attach it to an audio range sinewave generator.  Then get
right up close to the set and run the audio generator up into the ultrasonic
range.  When you get to the correct frequency, the set will respond.
Loudspeakers are very inefficient at these frequencies, so you will have to be
quite close.  By tweaking the generator knobs, you should be able to determine
the four frequencies of interest.  Once the frequencies are know, you can write
the code to generate them.

Note:  As kids we could get these sets to change channels by jingling keys or
blowing into the whistles that came with Captain Krunch!!

1997\10\07@184228 by Mike Keitz

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On Tue, 7 Oct 1997 12:10:12 -0400 John Shreffler <johnsspamKILLspamAVENUETECH.COM>
writes:
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>
>The old Magnavox (circa early 60s) remote created a supersonic
>whistling by pressing one of several bladders, like a dog whistle.
>It isn't a medium that could be converted to a digital encoding,
>I would guess.

The early Zenith remote sender had resonant metal rods inside.  When the
user pressed one of the buttons, a hammer would strike the corresponding
rod and ultrasonic sound came out the front.  The rods were differnt
length, thus each one produced a different frequency.  The frequencies
were not that far apart, due to the limited response of the receiver
transducer.  At the TV end, the signal from an ultrasonic microphone was
amplified and applied to a bank of filters.  Each filter had an envelope
detector, when the signal at that frequency was strong enough an action
would be taken.

The different frequency system is easily falsed by jingling keys,
clanking glasses, etc.  It was still an improvement over the
radio-controlled ones which would respond to your neighbor's remote as
well.  I think there were a few that used a digital code over ultrasonic,
but this was very short-lived, as IR soon replaced it.

If it only had 4 buttons its probably using different frequencies.  You
can generate the frequencies with a PIC but the transducer would like to
have tens of volts of drive, so a transformer maybe driven by a
transistor amplifier would be needed.  On the other hand, if you're
placing the converter close to the TV then only a very weak ultrasonic
signal would be necessary.  You might consider testing with a 555 timer
or signal generator circuit to see if the TV will respond to a simple CW
signal, and what frequencies are required.  The 40 KHz range was usually
standard for this.

>{Original Message removed}

1997\10\07@185258 by Harold Hallikainen

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On Tue, 7 Oct 1997 12:42:17 -0400 Steve Smith <.....XYGAXKILLspamspam.....AOL.COM> writes:
>>I was looking for some information on how the old TV remotes worked
>that
>>used ultrasonics for the remote controls.
>
>Try rattling a bunch of keys this often opperates these aincent tv's
>.I bin'd
>mine over 15 years ago.


       And a neighbor retunred a new ultrasonic pest repelling system
cuz it kept changing channels on his TV.

Harold

1997\10\07@195057 by dporter

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The Zenith was one of the first.  The remote had two aluminum bars that
were struck by a spring loaded button.  The button had two sides, much like
the +/- channel buttons on today's remotes.  You really had to press hard
for the hammer to strike the things.  While humans couldn't hear the tone,
you sure could tell that the damn thing was pushed.

A microphone was on the front of the TV to pick up the ultrasonics.  I
don't know the frequencies involved

----------
{Quote hidden}

1997\10\09@144955 by Larry G. Nelson Sr.

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It may not me too bad. I remember changing the channels on one of these by
dropping change or keys on the rug.


At 12:10 PM 10/7/97 -0400, you wrote:
>The old Magnavox (circa early 60s) remote created a supersonic
>whistling by pressing one of several bladders, like a dog whistle.
>It isn't a medium that could be converted to a digital encoding,
>I would guess.
>
>{Original Message removed}

1997\10\09@171723 by athan Jhonson......KC7JHO

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>>2) How would I create an ultrasonic sound using a PIC?


Just use a 567 to produce the sound and a pic to interface the all in 1
remote? ot to sure but it might work.
KC7JHO
ICQ# 3044899
Amateur Radio, It's not just for Talking any more!

1997\10\11@141902 by Andrew Russell Morris

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At 08:57 AM 10/7/97 -0700, you wrote:
{Quote hidden}

I have an old Zenith TV with a service manual. It uses about 6
electronically generated tones. If yours is a Zenith, I can look up the
frequencies for you.

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