this file was taken from USENET group misc.security everything you wanted to know about infinity transmitters -*-*-*-*-*-*-*-*-*-*-*-*-*-*- Date: Wed, 25 Nov 87 13:09:33 EST >From: Dave Kucharczyk Subject: Re: Infinity Yes, infinity transmitters do exist. they work on the principle that the audio path is made even before a dialed phone starts to ring. one sends a tone down the line which tells the infinity transmitter to "pick up" the phone before the ringing starts, and can then listen to teh location where the bug is planted. however these devices are pretty much made obsolete by the fact that any of the ESS switches do not open an audio path untill they receive answer supervision from the dialed end. ssr -*-*-*-*-*-*-*-*-*-*-*-*-*-*- Date: Thu, 26 Nov 87 11:51:35 EST >From: Larry Hunter Subject: Re: Infinity Ever heard of an "Infinity Transmitter"? Yeah, they are pretty old tech bugging devices. They used to work fine, but with the advent of separate signalling and voice circuits in ESS (the electronic version of Ma Bell's switching system) they became obsolete. The idea was that the bug would listen to the phone line for a tone. When it heard the tone (or combination of tones -- they were called harmonica bugs because people often used harmonica notes to trigger them) it would pick up the phone and you could listen to what was going on in the room that the phone was in, before the phone rang. The problem in ESS is that the caller is not connected to the line when it is ringing -- the audio connection is only made when the phone is picked up -- so the bug cannot hear the incoming tone. No audio path to transmit the tone, no infinity bugs. One might imagine more sophisticated versions of the infinity bug; It could pick up the line WHENEVER it rings, check for the tone, do the infinity bug thing is the tone is present and if the tone weren't present it would have to generate its own ringing voltage (for the phone) and ringing tone (for the caller) until the line really got picked up. As you might imagine, the ESS infinity bug would have to be much more complicated (read more expensive and more likely to be detected) than the old style ones. I've never heard of anyone trying this. There are lots of telephone exchanges that are not ESS (step and crossbar are the two main alternatives) where the simple old infinity bugs still work fine. Any exchange where "Custom Calling" (e.g. call forwarding or call waiting) is not available is probably not ESS. People still sell things like infinity bugs as "home baby sitters" or as burgler alarms, but they answer the phone all the time even though they only turn the mike on if they receive a tone. These are usueless as bugs because no one can make calls TO the target -- the bug always answers the phone. You can rest easy re: infinity bugs, although you should be aware that it is a pretty trivial task to use electronic surveillance these days and that a lot of people do it. Larry -*-*-*-*-*-*-*-*-*-*-*-*-*-*- Date: Sun, 29 Nov 87 16:27:38 EST >From: Mark W. Eichin Subject: Infinity Transmitters I saw an article on these once (on a bboard that got closed down about a year later for phone credit card postings). The main idea was that someone who wanted to tap the room would add this little circuit board to the phone, which would detect some sort of tone on the line when the phone first rang, inhibit the ring, and open the microphone. Something was mentioned about ultrasound (unlikely, given the quality of the phone lines, but it was being vague), and how you could tap in from anywhere as long as you could dial direct (ie. even from England). The main flaw was that the phone was of course busy (to the outside world) the whole time you were monitoring. It was allegedly used extensively by PI's to gather ``evidence'' for divorce proceedings. The article did not have much in the way of technical detail; oh well. Mark Eichin -------