Drop call seconds (drop SLA)
How long VICIdial holds an answered call waiting for an agent before it counts as a drop.
Drop call seconds is how long VICIdial will hold an answered call waiting for a free agent before it gives up and treats the call as a drop. It is the drop_call_seconds setting on the campaign, and it is the timer that turns "the dialer got lucky" into a recorded abandoned call.
Where the number comes from
Two different numbers get called the drop SLA, and it helps to keep them apart.
The FCC's rule is the one with legal weight: a telemarketing call counts as abandoned if a live representative is not connected within two seconds of the called party finishing their greeting. That is the definition regulators measure you against.
The campaign setting is what your dialer enforces. drop_call_seconds on vicidial_campaigns is a small integer, and the schema default is 5. Inbound in-groups have their own drop_call_seconds on a completely different scale - the column default there is 360 seconds, because it is measuring how long a caller waits in a queue, not how long a dialer holds a surprised human on an open line.
What happens when the timer expires
drop_action on the campaign decides. The options are HANGUP, MESSAGE, VOICEMAIL, IN_GROUP, AUDIO, CALLMENU and VMAIL_NO_INST. Silent hangups are the worst outcome available to you - the person answered, heard nothing and now has a complaint to make.
Playing a message instead is what the FTC's safe harbour contemplates: a recorded message that promptly identifies the caller and states the call's purpose. VICIdial ships the plumbing for it as safe_harbor_exten (default extension 8307) and safe_harbor_audio. Record your own audio and point those at it rather than shipping the placeholder.
Setting it sensibly
Shortening the timer does not reduce abandonment - it converts near-misses into clean drops faster. Lengthening it does not help either, because a person holding an open silent line hangs up anyway, and the regulator's clock ran out long before yours did. The real lever is pacing: your auto dial level is what decides how often you run out of agents in the first place.