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Dialer pacing and answering model

Every outbound dialer campaign answers three questions — who dials (claim mode), when each contact becomes eligible (enrollment ordering), and how fast the list can run (the abandon ceiling for predictive mode). This page documents each axis and the tenant-owned controls behind it. All outbound voice dials originate through the Devotel softswitch; the pacing model below governs when and how quickly those dials launch.

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The four claim modes

A campaign’s mode decides which surface claims its contacts. preview is the only mode driven by the GET /dialer/next-call endpoint — for progressive, predictive, and agentless campaigns that endpoint returns 204 No Content, and the pacing scheduler ticks every 30 seconds for the active campaigns on your tenant.

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Enrollment and ordering

Every contact row carries a next_attempt_at timestamp. Both claim paths — preview polls and the scheduler tick — order by next_attempt_at ASC and only pick up contacts whose timestamp has arrived. Upload ordering is therefore fully under your control:
  • Default. List upload stamps next_attempt_at = now(), so the whole list is eligible immediately and the list dials top-to-bottom in upload order.
  • Scheduled. Provide a specific next_attempt_at per contact at upload, or set one via a callback disposition, and the contact waits until that moment.
  • Best-time-to-dial (below). Stamps each contact’s predicted best window instead.
Retry logic writes back into the same ordering column: a failed attempt re-queues the contact at a backoff offset, and a callback disposition re-queues at the scheduled time.

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Best-time-to-dial

Set best_time_to_dial: true on campaign create or update (the value is stored in the campaign’s metadata). Contacts uploaded to that campaign are stamped with their highest-answer-probability window from the engagement engine — the same engine that powers optimal send time for messaging, evaluated on the voice channel — instead of now(). The claim path still just reads next_attempt_at; no hot-path change. Fallbacks chain in order:
  1. Cross-channel fallthrough. A contact with no voice engagement history gets the engine’s cross-channel aggregate (SMS or email history still yields a window).
  2. Local morning. A contact with no engagement history at all gets a timezone-aware local-morning window, resolved from the number’s area code where possible.
  3. Immediate. If the engagement engine is unreachable, the upload fails open — every contact enrolls with next_attempt_at = now(). Enrollment never blocks on the optional optimizer.
The federal TCPA quiet-hours gate still evaluates every dial at dispatch time in the recipient’s local time, so a predicted window can never push a dial outside the permitted calling window. See TCPA federal voice guard.

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The abandon ceiling

Predictive mode dials multiple lines per idle agent, which creates abandonment risk: a callee answers with no agent to take the call. The abandon rate is the fraction of connected calls abandoned; US federal rules cap predictive-dialer abandonment at 3% over a rolling 30-day window (47 U.S.C. § 227 / 47 C.F.R. § 64.1200(a)(7)). Two controls keep the campaign inside the ceiling. Both are organization-level settings — one value per account, not per campaign:
  • Default. With no override configured, the pacer governs against the FCC 3% hard cap.
  • Override. GET and PUT /voice/dialer-abandon-ceiling let you set a tighter ceiling (between 0.1% and the 3.0% FCC cap) as a percent — for example, pinning 2.5% for higher-quality lines. Clearing the override deletes the setting and the pacer falls back to the FCC default.
Semantic rules:
  • The FCC 3% cap is a ceiling control, not a compliance guarantee — the pacer clamps anything stored above it, and the auto-abort below is the actual enforcement layer. Your own legal posture still owns consent and list hygiene.
  • A warning signal fires when the observed rate climbs to 80% of the effective ceiling, before the hard abort engages.
  • Within safe bounds, a self-adjusting pacing ratio eases up when the rate runs comfortably low and throttles when it approaches the ceiling, keeping throughput high without breaching the cap.

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Auto-abort enforcement

When the rolling 30-day abandon rate crosses the effective ceiling, the campaign flips to status: "aborted". That state is terminal — no further dials launch, and the campaign can’t be re-activated. Create a new campaign after reviewing the abort reason. The abort guard is the legally safe response; pacing adjustment alone is not relied on to recover a breach.

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How dispositions write back into pacing

The disposition an agent (or the dial-status webhook) submits decides whether and when the contact re-enters the pacing queue:
  • Terminal outcomes — connected outcomes (sale, no_sale, voicemail, interested, not_interested), wrong_number, dnc, and carrier failures — close the contact out of pacing.
  • Callback — callback / callback_later sets next_attempt_at to the scheduled time; pacing re-picks the contact then.
  • Retry — failed attempts re-queue the contact at an increasing backoff until the per-contact max_attempts is consumed, at which point the contact is exhausted.
  • DNC — a dnc disposition also writes the phone into your tenant-wide blocked list, so every campaign’s pacing tick skips it from then on.
The full disposition-to-status matrix and the submission endpoint are documented in Dialer dispositions.

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See also