Parallel dialer vs. predictive dialer

Who the lines are for

Both open more lines than there are conversations. The difference is the denominator.

A parallel dialer opens, say, four lines for one named rep who is sitting there waiting. There is always exactly one person ready. If one call is answered, it goes to them. If two are answered simultaneously, one has nowhere to go.

A predictive dialer opens lines for a floor of agents and uses a model of how many calls will be answered to dial ahead of who is free. It is deliberately dialing more numbers than it has agents, on the statistical bet that enough will fail. It is a call-centre instrument, built for volume against consumer lists, and when the model is wrong the person who answers meets silence.

What the rule actually says

The FTC’s Telemarketing Sales Rule is specific, and it is worth reading in the original rather than in a vendor’s paraphrase.

An outbound call is abandoned "if a person answers it and the telemarketer does not connect the call to a sales representative within two (2) seconds of the person’s completed greeting" — 16 CFR 310.4(b)(1)(iv). Abandoning calls is prohibited.

There is a safe harbour, at 16 CFR 310.4(b)(4). It requires technology that ensures abandonment of no more than three percent of all calls answered by a person, measured over a single campaign of under 30 days or over each successive 30-day period; that each call rings for at least fifteen seconds or four rings before disconnecting; and that where no representative is available within two seconds, a recorded message promptly plays giving the seller’s name and telephone number.

Note what the three percent is measured against: calls answered by a person, not calls placed. On a list with a 10% connect rate, three percent of answers is a much smaller number than three percent of dials — which is the arithmetic most people get wrong in their own favour.

This is a plain-English summary of a published rule, not legal advice. Whether the Telemarketing Sales Rule covers your calls depends on facts about your business and who you are calling, and that is a question for your counsel rather than for a dialer vendor.

Why parallel dialing is not exempt

The tempting argument is that a parallel dialer always has a rep waiting, so it never abandons. That is true right up until two people answer at once, and then it is false in exactly the way the rule describes: a person answered, and no representative reached them within two seconds.

The exposure scales with your line count and your connect rate together. Four lines on a list where nobody picks up produces no abandoned calls. Four lines on a well-verified mobile list at a 20% connect rate produces simultaneous answers regularly. The better your data gets, the more carefully you have to run your dialer — which is the opposite of the intuition most teams have.

A dialer worth buying measures this and shows it to you. Ask any vendor for the abandonment rate their system produces at the line count they are recommending, measured against answered calls. It is a question with a number for an answer, and the answer tells you whether they instrument it at all.