RS-232 to TTL level converter

[Murtadha]

Hello Dear,
I'm a new student and I have a project. I designed a circuit to convert from RS232 to TTL which I will use fiber optic, but unfortunately it's not working. it's a very simple circuit, I found many circuits in the internet and they used MAX323, but my circuit is more easyer.

This is my circuit : http://www.tildesign.nl/rs232_ttl_converter-20107101P2N

 http://www.tildesign.nl/track/content/downloads/rs232_ttl_converter_schematic_and_layout.pdf

Anyway, As I know serial port transmit from pin 3 but when I checked pin 3 there is no volt.
My question is how to get volt from the serial port?

I have a program in C language to transmit TXT or FILES from a computer to anther via RS232 and fiber optic, Can I check it in Multisim? Or How can I check the serial port? please

Final equestion: in the circuit they used ICL3221, I tried to find it in the Multisim but I didn't find and I used MAX3221, it's same ICL3221 but without inverter in FROCOFF pin and EN pin, So Must I put inverter to MAX3221 at these pins? or no need? Do u advice me to use this IC ?

I'm a new student I hope the answer will be like in step by step please.
I'm using Multisim 10
 
 
Regards,

[KateB]

1. How to get volt from the serial port?

- Probably check it with Oscilloscope.

2. Can I check it in Multisim, or How can I check the serial port?

- Do serial loop back test: http://zone.ni.com/devzone/cda/tut/p/id/3450

3. Do u advice me to use this IC?

- Check with Maxim whether they provide SPICE model for this IC, and add it to Multisim. Check in Multisim manual on how to add it.