Program does not start

I run our main application from init.d/rcS.
I changed the debug channel to use the serial ttySAC2 console instead of 
the default ttySAC1 in the liniux_cmd_line.
Sometimes the program does not start when the RS232 converter is not
connected evidently because of noise on the RX line.
Has anyone had the same problem or knows a software method to switch the
console on only when needed?
 When posting my previous message I received an error and unintentionally
sent it twice.
 If anyone has any ideas I would be grateful.  
In the end, I would like to view the debug information also by telnet.

Thanks