logic mosfet instead relay to in central phone
I want to have a inter communication between two phone


You don't need relays or mosfets - a current source of about 50 mA should power both phones providing that it can sustain a terminal voltage of about 10 volts or thereabouts. The hook switch in each phone will disable the communication.

Normally, in old phone systems the current source is provided from 48 volts through a 300 to 500 ohm relay coil but you can use a resistor if you don't mind a little bit more sidetone in the earpiece. In more recent PBX systems I've seen 25 mA current sources made from bipolar transistors and a few resistors.