Hi all,
Now swear i did lots of search before posting this question here...also i went through the book on telephony by fried but did not get any datasheet or reliable results.

Now i don't want to connect a key pad directly with controller, there are examples in scott macanzine book on 8051 about keypad only... but not related to my problem.

Objective:-

1) When ever the power is turned on of my hardware , 000 appears on three cc 7 segment digits.

2) Using only one Telephone Set pulse dailing not DTMF. When ever the Telephone set goes off-hook and dail digits from 100-116 its corresponding number i.e. if 100 s pressed from the key pad of pulse dailing telephone set 100 appears on 7-segment and similarly other digits range is from 100-116.

Desired Method:-

I want to use serial communication to transfer data via txd and rxd pins of controller to the 7 segment , i know i can do it the other way but its my requirement...so can i use the same three 74LS373 for three digits but what components i need for serial communciation ? As i have to use the controller ports for some other purposes too

Tools :-

1) three 7 common cathode digits.

2) One Pulse Dialing Telephone Set.

3) C828 NPN transistor , 5 volts Dc Relay.

4) 18 Volts Dc Power Supply with 330 ohms resistor to operate a telephone set. 5 volts will also work i need to use 18 volts as in future some conversation work is also required. not at this stage.

5) three 74LS373 .

Main Problems:-

1) I don;t understand how to connect the telephone with the controller pins like i cannot connect directly one wire on P1.0 and the other to ground as telephone is also supplied with 18 Volts Dc. I just have any idea that some how relay & transistor will do the job but how?

2) Serial communication IC, do i require or some programming method can be used for this..