There may be no mob briefing. Usually they send you a letter
informing you of the manning, what to bring and pack etc.
Not in my case. They usually did the general mob briefings at
the tailend of my ICTs, but I was also regularly called back - as a
recall i/c - to attend half-days briefings in case it's a silent
mob. During the latter times, I often see a few unfamiliar
reservists - presumably temporarily attached or newly posted to my
unit - being pulled aside to get their own general mob briefings.
Some of them stood out cuz they were really "old birds",
complaining to the SAF regulars that they're too old to be
targeted, that they can't understand the English-language
regulations, etc.
You have to prepare a standard fullpack in both cases.
Actually I've never packed a standard pack; ditto my kakis. We
brought in what we usually bring for our ICTs, albeit with prior
networked knowledge of whether it's only a sign-in, or draw-arms,
or move-out activation. The officers, KAHs & others who
reported very early would spread the word by phone (if it's
something out of the ordinary). I remember us being caught out only
once on the "standby" regimentation, but they didn't formally check
the equipment until the M+6 hour was up, so there was some
last-minute scrambling to bulk-buy items. Even then, I don't recall
any formal scolding on incomplete equipment either. Probably can't
say the same for our CO, though.