DTMF Decoding

Hi,

I'm trying to use the MT8870 DTMF decoder to decode DTMF signals from an RJ11 Phone Jack. I'm from Trinidad and use the same DTMF 2500 telephone set like in the United States if i'm not mistaken. I'm using the decoder in the differential input layout as shown in the datasheet but i think i would need to know the tone timing durations (busy tone, dial tone etc...eg. 0.5s on/0.5s off) in order to calculate the values of capacitors and resistors to use in the differential input configuration shown. Does anyone know where i could find these tone timing durations?...I've search and searched and searched but can't seem to find it anywhere.

Am i going about this the correct way? i.e. to know what values to use for resistors and capacitors in this differential input configuration?

The MT8870 decodes the dialing touch-tones from a telephone, not busy tone nor dial tone from the telephone central office. It notches out the North American dial tone.
The differential input uses capacitors calculated to pass the lowest frequency (607Hz) touch-tone. The resistors determine the input impedance and the gain.