#pragma num_alias_table_entries 14

IO_1 output frequency clock(3) freq_out;
IO_4 input bit s1;
IO_5 input bit s2;

when(io_changes(s1)to 0) //sound of up, down and enter
{
	io_out(freq_out, 50);
	delay(6000);
	io_out(freq_out, 0);
}

when(io_changes(s2)to 0) //sound of esc
{
	io_out(freq_out, 80);
	delay(6000);
	io_out(freq_out, 0);
}

    Source: geocities.com/hk/cloud_fan_school/Program/Frequency

               ( geocities.com/hk/cloud_fan_school/Program)                   ( geocities.com/hk/cloud_fan_school)                   ( geocities.com/hk)