textfiles/phreak/WIRETAPPING/caller

NOTES ON RECORDING CALLER ID signals ....(AND VOICE NOTES)

There have been a number of people who have complained that caller
id is not working perfectly in their area. I have been working
with ZyXEL to try to get it and distinctive ring working perfectly.
It now does work in most of Canada and the US. 
Caller id works great combined
with distinctive ring.  
I enjoy such features as, if the modem encounters a busy bbs, it
sets distinctive ring to answer a CALL return (another feature
from the phone company), then answers in originate mode.  Thus you
can make contact with the bbs at the first opportunity after the
line clears, and not have your modem be disturbed by other calls.

For those (hopefully few) people who still have problems with 
caller-id,  here is a simple way to get information to allow
these problems to be resolved more quickly.  In the past I circulated
a circuit to do this.

However, thanks to the new voice features, there is an easier way.
The idea is to record the ring/callerid signalling on a voice file
which can then be listened to, and uploaded to the engineers
if necessary.  This also allows the cadence of the distinctive ring
to be measured if necessary.

It is REALLY simple to do also and is fun because you can even
listen to the signal and get a bit of an idea what might be wrong,
even without sending in the file.  It is also instructive to
write a little voice display program to become more familiar with
this format-- since the signals are predictable, monotonic, and
thus relatively easy to analyse with a simple program.

One of the problems is that some exchanges do not seem to follow
the Bellcore specs for callerid.  The way it is supposed to work,
is that after the first complete ring (or distinctive ring) 
stops, there is a 500 ms
pause, then a 250 ms section of "continuous" 
U characters sent (called a channel seizure signal), then a 150 ms
section of mark sent, then the data.  A simple number will take
about 200 ms further.  Then silence reigns until the next ring.

Now the tones used are 1200 hz for the mark or 1 bit, and 
2200 for the space or 0 bit.  Data is sent at 1200 baud in
an asychronous mode.  (this is called bell 202 standard).

Now the The U character is interesting in that it is 1 bit on ,
one bit off. 
Thus when it is being sent in a continuous mode, it also looks
like 250 ms of the frequency shift keying signal shaped as
a 600 hz square wave.   What does this mean??  it means that
it sounds like a quarter second of 600 hz tone.

So you should hear a ring, a 1/2 second of silence, a 1/4 second
of 600 hz (fundamental) tone, and then a quarter second
of 1200 hz tone-- followed by a short blast of a higher note.

What can go wrong??  1st, one problem is that some switches don;t
have a proper pause.  you might get the U's not sent continuously
which might sound like a lower note.  Third the mark might not
be long enough.  next the frequencies may not be correct.
The data can come slowly--with up to 2 characters of mark
signals between data. (according to the spec).  Thus you can
give ZyXEL some information without sending the file.   Your local
exchange sends all these notes (they are not sent from long distance),
so they are not attenuated very much.
Please also try to find out what kind of switch the exchange has. This
information can often be obtained from 611 repair service from a
nice teckie. Another interesting thing is some of these switches have
more than one way caller id can be sent.  They may just be set to
do it the non compliant way!! perhaps the technical people do not
know they have a choice.

Once you have the voice file,
Another crude way of timing, is to use a hex editor, and lop off pieces
from the end of the file (checking for the shielded code--and
preserving shielded data--make sure the file is properly terminated).  
this way you can listen do some timing
by looking a t the size of the lopped off file.  You can even look
at the raw data, and get the idea which area you are in. (espec
in 2 bit mode).
A less crude way, is to write a little program-- hey and what better
way for all you folks wanting to write a voice mail system to
force yourself to get started!.  You can convert the voice file
into one readable by some of the standard voice/oscilloscope 
sound blaster type programs. so you can see it on your screen.

The idea is to find out what went wrong, tell ZyXEL and provide
a backup recording.

Now-- you may ask,,  how do I get started.  WELLL,,  there is 
a little trick.  You need to read the signals without actually
answering the line.  The best way to do this is to fool the 
phone company into thinking you have not answered the line. 
One very easy way to do this is to get a capacitor and put it
in series with the line.  I found a .68 microfarad 400 volt 
non polarized (ie no + on one of the terminals) 
capacitor (eg from radio shack).--just a cheap
mylar capacitor (could even  be 200 volts). (but
.22 - 4 microfarad also seemed to work).    and put it
in series with the line.  ONe  easy way to do this is to modify
your wall plug (which has screws ).  Unscrew one  red wire,
and put a capacitor in series with it and the other red wire 
formerly going to the same terminal.   You may want to leave 
an extension phone plugged in on another outlet so you can
hear the ring (and answer any calls you get while playing).

Now bring up your zfax and select the voice utilties.  pick
record voice and select the telco line.  then before starting
the recording by pushing enter on the OK message,
 have someone dial your phone. press enter about the time they
have finished dialing your phone.  This will creat a nice short
voice file.  PUSH ESCAPE as the second ring starts.  This
should create a nice 30k file or so with all the info on it.
Then play back the voice and start analysing.  You should be
able to hear it as well as a regular call on your internal
modem speaker. The ring will sound like a blast of sound--but
not too loud and you should hear a beat of nothing (.5 sec) then 
beeep(600hz,1/4 sec) beep (1200hz 1/8 sec)  bep (1800-2400hz 1/16 sec).    

 I am interested in any voice software people do also.  Please
send me a note if you have some success.  I would also love to
supply you with a ZyXEL modem, esp if you are in Canada.
(I can provide  extra callerid software also)

George Vande Bunte   PENG
OCOMP
416 5341508  gvb@telly.on.ca 
238 Davenport Rd. Toronto m5r1j6

Please keep whole file together.