Dear Andy Neil,

Thank you, Now I know what Ctrl Z is,
I'm using hyperterminal in windows environment.
The language is C, and I'm using C51 from Keil.

Any way, in your previous suggestion,
you suggested me to set the phone receiving mode
to "terse" mode, would you please show
how to do set the gsm to terse mode.

The message just simple

unsigned char code over_heated [] =
{'Over heated at section 1',0x1a, 13,10,0};

Again, thank you Mr Neil. Your explanation is helpful.
Kurnia Brahmana