Autoscan --> motorola LS1203 scanner

Does someone knows how to prevent LS1203 scanner to enter in "sleep mode  
" ?. I have set auto scan mode to scan continuously, but after some time  
of inactivity, scanner will enter sleep mode.

The problem is that this should be fully automated and closed system,
so user will have no access to scanner.

We have used this scanner before and it has worked for few months  
without entering sleep mode , but i can not remember how to make this...

GM