Ann: Trading Halt, page-35

ASX wants company to go into a 2 day TH as soon as they feel that there is something concrete happening that is material to the sp... they can always announce any time before the 2 days TH... and if the deal is not finalized in the next 2 days while in TH, the term "suspension" is used to extend the tradin halt and the only difference is now to purge all orders...

that 2 day TH is almost always sufficient to come out with the expected news in time... with some companies dealing with overseas entities, there may be a day or two of extensions due to time differences and some dotting of Is and crossing of Ts...