telephone conferencing equipment

[orpheus]

heyy,
i'm a final year electronics and communication student doing a project on party line system, telephone conferencing equipment.
i am looking for dtmf decoder circuits ...........i already have a circuit that uses a mt8870b(dtmf decoder) ic along with shift registers n compators.but i'm lookin for more smaller circuits for my designs.
also i'm lookin for circuits that do on hook - off hook detection for telephone instruments.

 

[fredsm]

How complicated? I have circuits that range from using 567's,
to using dedicated pass/reject discrete filters, and to complex
filtered A/D converters, and dedicated DTMF decoder IC's.
<als>

 

[orpheus]

dtmf

dtmf decoder with a/d convrtr or dtmf dedicated ic's wud do.......