This is a program used for CCIR tone detection used for
selective calls. Used by for instance by the swedish
police force.

It does this by discrete Fourier transform (DFT) utilizing 
the Goertzel algorithm. The samplerate should be as low as 
possible as to get as good resolution in DFT as possible 
and N is selected to get as good "hitratio" as possible on 
the actual frequencies.

I selected 8kHz samplerate and with help of calcN.m I used 
Octave to calculate N (288).

Build it by running make.

You can select which inband tone system you want to detect by 
changing an option the program:
-c: CCIR
-z: ZVEI
-e: EEA
-i: EIA

CCIR is default if no option is given.


Only tested on Linux. How it works for other operating
system is unknown, though considerations to make it as 
Posix compliant as possible has been taken.

The files are:
* README.txt: This file.
* audio.[hc]: Soundcard sampling setup, taken from another 
  project of mine, ape (http://ape.sourceforge.net/).
* tone.c: The main program for actual tone detection.
* calcN.m: Octave program for evaluating a nice value of N.
* ccir.m: Octave program to verify the Goertzel algorithm 
  on CCIR tones.
