13 January 2000

Date: Thu, 13 Jan 2000 12:07:38 -0500
To: "B. J. Crosby" <brentcros@home.com>,jross@rosseng.com
From: "James A. Ross" <jross@rosseng.com>
Subject: Re: Baby monitor

At 08:42 PM 1/12/00 -0600, you wrote:

>Jim:
>
>I always enjoy receiving your newsletters.....we seem to share the same
>views on much of today's government activities.....I know you are busy
>and hope you can give me a brief reply.....it does not have to be brief.....
>
>In your most recent issue you wrote about Hit #1 as being a baby
>monitor.   My question is why would a low cost baby monitor be an
>excellent source for audio transmissions, as compared to other high tech
>audio systems?  I have admitted in the past, this is a fairly new field
>for me, but getting a great deal of my attention.
>
>I guess my questions is also, why would one buy a video/audio
>transmitter/receiver, then only utilize the audio portion of it?
>
>I am sure there is a good solid answer, but I can't learn if I don't ask.

Bing,

Your question is a very good one - so good, in fact that I'm sending this response to everyone on my list.  My thought is that, if this technology is new to you, it must be new to many of those on my list.  So, here goes.

My comments in my newsletter related to a carrier current baby monitor that had been repackaged to make it look like a power supply for some piece of electronic equipment - not attached at the moment.

First, this type of radio transmitter has a very low frequency output - usually somewhere in the 100 to 200 KHz range.  Such a low frequency means that its signal tends to stay on the wires it is connected to rather than radiate through the air.  It does NOT transmit video, only audio.  For the moms and pops who use 'em, it means they can hear baby's cries anywhere in the house by merely plugging the receiver in to the power line.

In the case I described in the newsletter, the target of the eavesdropping attempt became curious as to the purpose of this box plugged into the wall outlet near his desk.  When he unplugged it, nothing stopped, so he sent it out for analysis; and the report we covered in our newsletter explained just what had been done to make it look like a power supply for some unknown piece of electronic equipment while it was actually transmitting his conversations to a remote listening post somewhere else on the same side of the serving power transformer.

Carrier current is the name generally given to this type of equipment, but it is sometimes called "line carrier".  It is mass produced, so the purchase price is very low, normally under $50 for BOTH the full set of transmitter and receiver.  I've been told that the FBI used carrier current to get John Gotti, and, if so, I commend the FBI for finally discovering carrier current.  And I'll bet you dollars to doughnuts that John Gotti's TSCM man is now wearing concrete boots at the bottom of the Hudson River.

OK, let's get to some facts.  Carrier current works very well.  It is inexpensive, and easily obtained. It provides good quality audio reproduction at the receiver.  Normally, the receiver must be on the same side of the power transformer in order to receive the signal from the transmitter.  However, it is possible to put a jumper capacitor across the transformer, and this will allow transmission beyond the transformer.  In fact, during WW II, hams used to rig up nets than ran all over town because they could not go on the air in the normal fashion.

Do you see carrier current when using a spectrum analyzer in TSCM?  The answer is: "Normally No."   That is due to the fact that the power input circuitry in the spectrum analyzer has filter to keep any RF on the power line out of the analyzer - where it could interfere with the function of the analyzer.

Do we check for carrier current when we do TSCM?  The answer is: "You bet your boots we do.  We use a  custom-designed low frequency receiver to check power lines, phone lines, and any other conductors that might be carrying carrier current."  (For more information on this, see our web site at http://www.rosseng.com.)

Why is carrier current an important threat?  The answer is three-fold: 

1.  "Excellent quality carrier current is inexpensive." 

2.  "A carrier current transmitter can be hidden in anything connected to power." 

3.  "Many 'professionals' who do 'debugging' have never heard of carrier current."

Bing (and any other reader of this email), if you have any other questions, please email them to me.

Regards,

Jim Ross