I need to interface to 3 telephone lines using one circuit and detect any dialed numbers on any of the three lines and send each dialed digit it to rs232
Also disconect line when need to.
Can add more lines to reach 8 lines in future.
LCD same thing
i think you will ring detector to each line and the output of ring detector open the line to the caller ID cit you may need analog switches such as 4053 to make this multiplexing
HI
You can use IC CMX866 from CML Microcircuits.
It has inbuilt DTMF generator & a RS232 interfacing facility.
It also has inbuilt AT command interpreter with which you can dial/answer from PC.
I am also attaching PDF for CMX866
I hope this will help.
Bye