Would be good to get a recording of it. If I had to guess, I'd say it's something to do with adding a salesperson to the call. Imagine your agents are sitting

Would be good to get a recording of it. If I had to guess, I'd say it's something to do with adding a salesperson to the call. Imagine your agents are sitting there manually making calls and waiting for a pickup (preview dialling). That's time they could spend talking. Some outbound call systems will make multiple calls at once, then hand over to human operators once a connection is established on any of them (progressive or predictive dialling). The tone might be played as part of handing over a predictive call to an agent.