Failsoft means, short version, that the trunking controller has packed it in. The system is unable to generate a control channel or maintain trunking capabilities. All transmitters (or specific transmitters, depending on system configuration) will come active (keyed-up) and operate in conventional mode until the trunking controller comes back from its lunch break.
Failsoft is a pretty big deal in a trunk system. All users will be on one frequency (or a few frequencies, again, depending on configuration). There are no talkgroups, no extended features. You won't hear anything on talkgroups (at least, so I'm led to believe - my local system has never fallen over that badly - knock on wood!) because there is no control channel to drive the talkgroups. Look for one of the system frequencies to be "keyed-up" constantly - like I said above. All your traffic will be on there.
There is another failure mode called "site trunking" in a Motorola Smartzone system like Fleetnet is. Site trunking happens when the connectivity between one site and the rest of the network is lost. The site is still happily buzzing away with a control channel, but users on that site will not be able to hear anyone on the rest of the network, and vice-versa. This frequently can put units out of touch with their dispatchers. Some systems have talkgroups which are configured (at the end-user radio level) to only work on certain towers/sites - meaning that when you switch to that TG, the radio must affiliate with tower such-and-such in order to function. That ensures communication in a site trunking situation (so long as you can "see" tower such-and-such, and it's not the one in site trunking).
