[randycupertino]

This is because the autodialer won't assign an agent to your call unless it detects you picking up and speaking. At least, that is how it worked at my old call center, thank the lords I don't work there any more.

The bulk dialer would dial hundreds of numbers per minute, but we would only have 5-10 agents per shift sitting in the queue for outbound calls (most hated shift at the call center), so not worth it to have them all sitting there on the line while it's ringing.

That time period where it's dead air is the autodialer routing your call to an agent.

Same reason you get halfway through or cutoff voicemails from robocalls... they can't tell the difference between a voicemail and you talking so the robomessage starts playing before the voicemail takes the message.