"Joey" wrote in message
...
Suppose someone visited your office or home and tried to make a voice
recording using a hidden recorder.

If they used a older-style dictation machine based on tape then you
could detect the electromagnetic transmissions from the dictation
machine when it was recording.

But how would you detect if someone was secretly recording with an MP3
player that recorded to flash memory?

Is there some transmission which could be detected?
Perhaps some low power ultra high frequency from chip refresh cycles?

What is done is to generate a pattern of sound, only
part of which is audible, and then detect the low level
IF and RF that any sound equipment emits. Then follow
the signal detected to its source.

Luck;
Ken

"Joey" wrote in message

Suppose someone visited your office or home and tried to make a
voice recording using a hidden recorder.

If they used a older-style dictation machine based on tape then
you could detect the electromagnetic transmissions from the
dictation machine when it was recording.

But how would you detect if someone was secretly recording with an
MP3 player that recorded to flash memory?

Is there some transmission which could be detected?
Perhaps some low power ultra high frequency from chip refresh
cycles?

On 10 Oct 2006, Ken Maltby wrote:

What is done is to generate a pattern of sound, only
part of which is audible, and then detect the low level
IF and RF that any sound equipment emits. Then follow
the signal detected to its source.

Luck;
Ken


Generate a pattern of sound part of which is inaudible?

IF and RF?

"Joey" wrote in message
...
"Joey" wrote in message

Suppose someone visited your office or home and tried to make a
voice recording using a hidden recorder.

If they used a older-style dictation machine based on tape then
you could detect the electromagnetic transmissions from the
dictation machine when it was recording.

But how would you detect if someone was secretly recording with an
MP3 player that recorded to flash memory?

Is there some transmission which could be detected?
Perhaps some low power ultra high frequency from chip refresh
cycles?

On 10 Oct 2006, Ken Maltby wrote:

What is done is to generate a pattern of sound, only
part of which is audible, and then detect the low level
IF and RF that any sound equipment emits. Then follow
the signal detected to its source.

Luck;
Ken


Generate a pattern of sound part of which is inaudible?

Acoustic energy then, what the microphone/audio detection
picks up. (It will cover more frequencies that humans can
hear.)

The pattern is on at a particular time then off, it varies in
certain ways that will enable further analysis of any:
IF and RF?
Intermediate Frequencies (IF) or Radio Frequencies (RF)
given off by a device reacting to the pattern of sound.
If there is any IF or RF detected that corresponds/matches
the on off times of the pattern of sound, you know there is
a device responding to the sound in the room.

A more sophisticated analysis of the detected response
to the pattern, can provide a great deal of information
about the device detected. That would be beyond the
scope of your question, and your security clearance, as
well.

Luck;
Ken

On Tue, 10 Oct 2006 21:36:48 -0500, "Ken Maltby"
wrote:


Acoustic energy then, what the microphone/audio detection
picks up. (It will cover more frequencies that humans can
hear.)

The pattern is on at a particular time then off, it varies in
certain ways that will enable further analysis of any:
IF and RF?
Intermediate Frequencies (IF) or Radio Frequencies (RF)
given off by a device reacting to the pattern of sound.
If there is any IF or RF detected that corresponds/matches
the on off times of the pattern of sound, you know there is
a device responding to the sound in the room.

A more sophisticated analysis of the detected response
to the pattern, can provide a great deal of information
about the device detected. That would be beyond the
scope of your question, and your security clearance, as
well.


I'm not so sure this technique will work with an IC that has
constant current, continual encoding of even silence as a
typical MP3 player/recorder is likely to use. There might
be a theoretical difference but one far more difficult to
measure than even anything at all from the device.

"kony" wrote in message
...
On Tue, 10 Oct 2006 21:36:48 -0500, "Ken Maltby"
wrote:


Acoustic energy then, what the microphone/audio detection
picks up. (It will cover more frequencies that humans can
hear.)

The pattern is on at a particular time then off, it varies in
certain ways that will enable further analysis of any:
IF and RF?
Intermediate Frequencies (IF) or Radio Frequencies (RF)
given off by a device reacting to the pattern of sound.
If there is any IF or RF detected that corresponds/matches
the on off times of the pattern of sound, you know there is
a device responding to the sound in the room.

A more sophisticated analysis of the detected response
to the pattern, can provide a great deal of information
about the device detected. That would be beyond the
scope of your question, and your security clearance, as
well.


I'm not so sure this technique will work with an IC that has
constant current, continual encoding of even silence as a
typical MP3 player/recorder is likely to use. There might
be a theoretical difference but one far more difficult to
measure than even anything at all from the device.

You would be surprised at what is being done.
As one of my techs used to say. "Noise, what Noise".
But then this stuff tends to be kind of pricey.

"kony" wrote in message
...
On Tue, 10 Oct 2006 21:36:48 -0500, "Ken Maltby"
wrote:


Acoustic energy then, what the microphone/audio detection
picks up. (It will cover more frequencies that humans can
hear.)

The pattern is on at a particular time then off, it varies in
certain ways that will enable further analysis of any:
IF and RF?
Intermediate Frequencies (IF) or Radio Frequencies (RF)
given off by a device reacting to the pattern of sound.
If there is any IF or RF detected that corresponds/matches
the on off times of the pattern of sound, you know there is
a device responding to the sound in the room.

A more sophisticated analysis of the detected response
to the pattern, can provide a great deal of information
about the device detected. That would be beyond the
scope of your question, and your security clearance, as
well.


I'm not so sure this technique will work with an IC that has
constant current, continual encoding of even silence as a
typical MP3 player/recorder is likely to use. There might
be a theoretical difference but one far more difficult to
measure than even anything at all from the device.

You know how an IC gives off heat in relation to how
hard it is working, ("constant current" is a myth) heat is
only one part of the electromagnetic spectrum. Switching
devices certainly produce as much "noise" when they
operate as analog devices, more in most cases. We have
devices that can detect very, very low wattage signals.

Luck;
Ken

On Wed, 11 Oct 2006 00:38:03 -0500, "Ken Maltby"
wrote:


You know how an IC gives off heat in relation to how
hard it is working, ("constant current" is a myth) heat is
only one part of the electromagnetic spectrum.

No, constant current is a fact. The IC draws constant
current in many MP3 players and does not substantially
change it's heat output unless entirely turned off or put to
sleep which is an entirely separate mode of player
operation, not momentary in use like with a CPU.


Switching
devices certainly produce as much "noise" when they
operate as analog devices, more in most cases.

We may have a mic on shielded cable running to a constant
current chip that digitizes. It's spitting out digits when
there's no noise as well as when there is. Yes there may be
noise, but it may not vary as with the old analog, and
certainly not as noisey as something more obvious- a
transmitter signal.

We have
devices that can detect very, very low wattage signals.

That may be useful if you have an object in your hand, but
remember the unknown context of this thread, and that they
can't be constantly false detecting cell phones, beepers,
etc, providing the cell phone isn't recording off-grid which
is a whole 'nuther issue.

"kony" wrote in message
...
On Wed, 11 Oct 2006 00:38:03 -0500, "Ken Maltby"
wrote:


You know how an IC gives off heat in relation to how
hard it is working, ("constant current" is a myth) heat is
only one part of the electromagnetic spectrum.

No, constant current is a fact. The IC draws constant
current in many MP3 players and does not substantially
change it's heat output unless entirely turned off or put to
sleep which is an entirely separate mode of player
operation, not momentary in use like with a CPU.


No, contsant current isn't a fact. When an IC sends outputs the signals on
the traces are switching and unless the same data is flowing you will see
different currents depending on what data is bieng sent and what was sent
before. Resistance can also change.


---Matthew Hicks

"kony" wrote in message
...
On Wed, 11 Oct 2006 00:38:03 -0500, "Ken Maltby"
wrote:


You know how an IC gives off heat in relation to how
hard it is working, ("constant current" is a myth) heat is
only one part of the electromagnetic spectrum.

No, constant current is a fact. The IC draws constant
current in many MP3 players and does not substantially
change it's heat output unless entirely turned off or put to
sleep which is an entirely separate mode of player
operation, not momentary in use like with a CPU.


Switching
devices certainly produce as much "noise" when they
operate as analog devices, more in most cases.

We may have a mic on shielded cable running to a constant
current chip that digitizes. It's spitting out digits when
there's no noise as well as when there is. Yes there may be
noise, but it may not vary as with the old analog, and
certainly not as noisey as something more obvious- a
transmitter signal.

We have
devices that can detect very, very low wattage signals.

That may be useful if you have an object in your hand, but
remember the unknown context of this thread, and that they
can't be constantly false detecting cell phones, beepers,
etc, providing the cell phone isn't recording off-grid which
is a whole 'nuther issue.


Normally people entering rooms have to pass through
doorways. I would think any "open mike" that responds to
the pattern should be considered a threat.

But look, you can believe what you want, your world can
be a much simpler place, if you don't delve into these issues.

Luck;
Ken