Anyone who has listened in on cellular phone calls with a scanner or using the test mode of their cellular phone will have noticed a call suddenly dissappearing, after a short chirp. What is happening is the call has been moved to another channel. That chirp is a control message sent by the cell tower to the mobile phone telling it what channel to go to. All phones have built in hardware to decode this, and it is available in test mode in a great number of them. Here's how to decode this using a Motorola phone.

If you know how you use a C compiler, you can compile and run this tiny program after reading the below text.

Here's the program that someone compiled for MS-DOS. CTCCU is another DOS program for this purpose, it also does frequency to channel (and the reverse) conversions.

If you insist on a MS-Windows interface, MotChannel 1.0 is a windows application for this purpose. (caution! 3.5MB!). I don't recommend this program, many users have had troubles with it.

Or, you can do it the old-fashioned way, by hand:

HACKING THE FOVC

This hack assumes you can:

1. put your MOTOROLA phone into test mode.

2. unmute audio (08#)

3. load channel numbers until you find something worth listening to. (11XXX#, where XXX is channel number)

Problem:  When listening to something interesting (a conversation),
just when that sexy sounding horny broad begins to give her
phone number to some lucky guy, HANDOFF!!! then static... DAMN!
 
Trick:    Hack the FOVC.
 
    a quick definition:  FOVC  = FOward Voice Channel
                         FOCC  = FOward Control Channel
                         REVC  = REverse Voice Channel
                         RECC  = REverse Control Channel
 
As the phone travels through cells, the FOVC is where the tower tells
the phone to adjust power levels for the current cell or to change to
a new channel for use in the new cell. This info can be hacked apart.
So. When you've found a good conversation, don't be lazy! Enter 40#!
This makes the phone listen for commands on the voice channel
(embedded in the audio portion- you can hear it as a "bump" sound). It
will just sit there and the display will read '40' , but the
conversation will still be audible.  Now when the phone receives a
FOVC command (a 40 bit sequence) data will flow across the display, in
hex format, and stop. Listen to the phone, if the conversation is
still there, then the command was only to adjust power levels. If the
conversation is gone, then its a handoff. If you only got a power
adjustment command just press # or clr,  which ever gets you back to
the ' prompt. Enter 40# and keep listening. You can also use the # key
to cancel the 40# command, if you want to change channels or something.
 
 
If it was a handoff, its time for some quick math. You have to convert
some of the numbers to binary, and then to decimal. I don't know how
many characters your phone's display will show. Mine only shows the
last seven of the ten hex digits. Count left from the end 6 digits.
Write down that digit and the next two on a piece of paper, ie:
 
 
    ???j16djjj    j=junk numbers  (hex numbers range from 0-9,a-f)
       / \
      these are lost due to scrolling
 
       write down  16d then convert it to a binary string:
 
       1 = 0001
       6 = 0110
       d = 1101    (d=13)
 
       now you have a binary string like this:  000101101101
       throw away the first 2 bits and get:       0101101101
       convert this to decimal and get:                  365
 
 
365 is the new channel the conversation has moved to! Enter 110365#
and voila! You too, can hear the horny babe's phone number!
 
Don't forget to enter 40# again, as the call may be moving quickly
through cells ( small cells or freeway driving ) or the call can get
bounced around by the tower for cell traffic purposes.
 
Here's one more example of the hex>binary>decimal conversion.
 
        ???j5aejjj
 
        5  =  0101
        a  =  1010
        e  =  1110
 
        full string        = 010110101110
        truncate 2 msb     =   0110101110
        convert to decimal =          430
 
 
That's all for today! Anybody having similar hacks, please post!
 
Also, if anyone can help with the following questions, THANK YOU!!!
 
1.  What are the pinouts and specs on the MOTOROLA FLIP phone data
    jack?
 
2.  I know that three of the pins are a "proprietary" data bus. This
    comes from a tech at motorola. HOW DOES THIS BUS WORK???
 
3.  When loading channels into the synthesizer with 11xxxx#, the
    phone goes to a preset frequency for receiving and a different
    frequency (45 khz lower?) for transmitting. Can the frequency
    table be shifted to allow a phone in test mode to RECEIVE the
    REVERSE channels instead of only the foward channels???
 
 
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