Thanks to all beeper. many beeps received.

Hi Babar, I want 8051 to beep, not the buzzer by itself. For learning. My idea is to learn many things and put a lot of load on 89C52 (what I am learning on, or you can say leaning-on). I found it is very difficult to do but I learn more.

Sor far I have attached a 20 keys pad, An 20x2 LCD panel, IR TX and IR RX, Driving triacs with PWM, Switching ON/OFF eight electrical appliances, 24 hours Timer for all eight appliances, we can program on per minute basis for un-limited time turn on/off,

Software RTC, User interface for setting the RTC time and Timer data.

ETC ETC.

All above with one 89C52 without using any other chip or controller. Of course it would not be much if I was a Guru, but I feel I am still novice as 8051 can still do much more.

Now I want to do the two way communication using IR. I have developed my own (very simple) protocol for IR transmission. It is not 100 percent fool proof but so far it is working with me without any error.
There are still some tests remaining in order to test the accuracy of IR transmissoin using my protocol.

Jay's info is very interesting to me. I had the idea as many PEST control uses such technics in order to keep insects away from houses and from warehouses etc. But I had no spectrum idea. As I learned from some where (dont remember the source now) that a human ear can respond to 20Hz to 20KHz. I also seen at many multimedia speakers specifications shows frequency range from 20~15KHz and some upto 18KHz.
Thats why I was trying high frequencies above 10KHz. But now I will try to beep at 3KHz or lower.

Thanks steve, but making 8051 from sands dunes is very hitech yet to me, but thanks to Craig that what I learned from this forum, probably I was not able to learn in university in such period of time. One day we might change Sands into tiny 8051s.

Thanks to all again,

Rauf