modem communication

hi i m sam

can anybody tell me for what type of signal modem looks for , for communicating with other modem ?

anybody worked G.shdsl modem technology.........

Depends on the kind of modem.
Lets just say that it's a POTS (plain old telephone system) modem.
There are a number of standards from the old AFSK Bell tones through to some complex 64QAM systems.
And there are a whole family of protocols for how modems talk and agree with each other.

The 20th Century is but a memory for me now, so your question for digital palaeontology this is a good place to start:
https://en.wikipedia.org/wiki/List_of_ITU-T_V-Series_Recommendations

ADSL modems are not a lot different and communicate with each other in a similar fashion.

u got any flow chart of how the modem get connect ?

Nope, sorry, you'll have to consult the oracle... google.
Trying something like "V32 handshaking".