Theory of building a bluebox using about 6 DTMF dialer circuits.  In 
theory you could buy 6 DTMF dialers from radioshack, hook up wires to the 
pins corresponding to the digits on the DTMF IC inside the board and route 
the wires back to one keypad, each dialer having a different crystal for 
the needed bluebox frequencies, however you would only be able to produce 
bluebox frequencies 1,2,3,4,5,7,8,9,KP and KP2 and some green box 
frequencies(operator release and coin return, i.e. the Rad box, which 
works well using a 4.194mhz crystal, 5 is op release, # is return)  Here 
are the crystal frequencies for the bluebox tones, note you wont have 
digit 6 or ST, but perhaps you could find another way of generating them.  
Remember you can also use 6.5 or 6.5536mhz and use the * key for 
redboxing, or 8.194mhz and use the * key for CAS caller ID tone.  Some of 
these crystals may be hard to find or non-existent.  Use the 1mhz diagram 
at the bottom to calculate the crystal needed for your own 
frequencies.(the diagram shows what frequencies would be produced with a 
1mhz crystal., simply divide the frequncy you want by the frequency of one 
of the colum or row frequncies in the diagram.  I.E. for 2600hz do 
2600/337.75 = ~7.7Mhz, using this you can then do 7.7 * a row frequency, 
i.e. 7.7 * 194.7 = ~1500.  What this means is the digit 1 when pressed 
would be 1500+2600hz.  You can also use averages to try to get a certain 
DTMF frequency on the key you want, a good example would be the redbox, 
say you want the * key to be 2200+1700hz.  do 2200/337.75= ~6.51Mhz, then 
you want 1700hz to be the row frequency so you do 1700/262.88= ~6.47Mhz.  
You take the average of these 2 frequencies, so 
6.51+6.47mhz=12.98/2=6.49Mhz.  Thus you would want to use a 6.49Mhz 
crystal to get 1700+2200hz.  However this only works if the frequencies 
aren't too far apart, in this case 6.51mhz and 6.47mhz showed up as the 
frequencies you would want to make the * key 2200+1700hz, this isn't 
always the case though, i.e. if you wanted the * key to be 2200+1100hz 
you'd do 2200/337.75=~6.51 and 1100/262.88=~4.18, 
6.51+4.18=10.69/2=5.345Mhz.  However a 5.345Mhz would make the * key 
1805hz+1405hz, no where NEAR the frequency you want.  You could probably 
make a program to go through every combination and find the best possible 
average.. meh.)  Here are the crystal frequencies for a bluebox:

2.66mhz
#= bluebox 2
*= bluebox 1

3.42mhz
*=bluebox 3

3.25mhz:
4= bluebox 2
6=bluebox 4

3.85mhz:
7= bluebox 5

4.62mhz:
1 = bluebox 8/greenbox op release
2 = bluebox 9

5.11Mhz:
4= bluebox KP/greenbox coin return
*= KP2

Here's the diagram of a DTMF encoder using 1mhz:

           337.75   373.2   412.6
194.7    [1]         [2]        [3] 

215.1    [4]         [5]        [6]  

238      [7]         [8]        [9] 

262.88   [*]         [0]        [#]