Charles,
thanks a lot for replying me. Actually i want to use controller not any analog circuit.
I want to make use of a controller and other related to circuit to connect 2 telephone sets.

Now Suppose,

Charles has a Telephone Set "1"

Talhaz has a Telephone Set "2"

Both Sets are Pulse Dailing.

Both sets are not connected to any external telephone service .

When ever Charles Pick up his hand set he hears a Dial Tone Similar to that as we hear when we pick our normal telephone set connected to external service line.

At this Stage when charles set is off-hook if talhaz pick up his telephone set then he also hear a Dial Tone.

Now if Charles want to talk with talhaz he will dial "2" from his telephone set at this stage if talhaz telephone set is off-hook then only the both telephone sets get connected.

I know there are method to do the above without controller but i want to do the above using 8051 only.