> ## Documentation Index
> Fetch the complete documentation index at: https://docs.yotel.in/llms.txt
> Use this file to discover all available pages before exploring further.

# Dial modes

> How Yotel's three outbound dial modes — preview, progressive, and predictive — differ, when to pick each, and how voice broadcast fits on top.

Yotel exposes three outbound dial modes. They are selected per-campaign via the
`dial_mode` field on `POST /v1/campaigns`. Industry vendors use many overlapping
names for the same behaviours (power dial, auto dial, ratio dialer); this page
maps Yotel's canonical names to the terms you may already know.

## Preview

In **preview** mode, the agent sees the lead's details (name, previous notes,
last disposition) and manually clicks **Dial** to place the call. The dialer
does not originate the leg until the agent confirms.

**When to use it.** High-value outbound — B2B sales, enterprise renewals,
collections escalations — where the agent needs context before speaking. Also
the right choice for low-volume lists where agent idle time is not the
bottleneck.

**Industry aliases.** Preview dial. Sometimes called "manual dial" when there
is no lead-record preview step, but Yotel always surfaces the lead card.

## Progressive

In **progressive** mode, the dialer places exactly one call per available
agent. The moment an agent becomes idle, the next lead in the list is dialed;
as soon as the lead answers, the call is connected to that agent. Ratio is
always 1:1 — the dialer never over-dials.

**When to use it.** Mid-volume outbound where you want to keep agents busy but
cannot tolerate any abandoned calls. Good default for most Indian BPO
campaigns because it plays nicely with TRAI DND requirements and avoids the
regulatory risk of abandoned calls.

**Industry aliases.** Power dial. Auto dial. 1:1 dialer. "Power dialer" and
"auto dialer" are used interchangeably with progressive across most US/EU
vendors — Yotel's term is **progressive**.

## Predictive

In **predictive** mode, the dialer over-dials using an Erlang-B-based
ratio-aware algorithm. It places more calls than there are free agents,
betting that some will go to voicemail, ring out, or be busy. Answered calls
are routed to the next available agent via the ACD queue.

**When to use it.** High-volume outbound where agent utilisation dominates the
economics — telesales, lead qualification, survey, collections-at-scale. You
need a floor of roughly 20+ agents for the statistics to work reliably.

**Industry aliases.** Ratio dialer. Over-dialer. Predictive dialer. All refer
to the same basic shape: dial ratio > 1.0.

### How Yotel protects abandon rate

TRAI and most global regulators cap "abandoned" calls (answered by the lead
but no agent available within a short window). Yotel enforces a **hard 3%
abandon-rate cap** — this is non-negotiable and built into the predictive
engine itself:

* The dial ratio is continuously recomputed from rolling answer-rate, AHT, and
  agent-available stats.
* Each campaign has `predictive_target_abandon` (default `0.025` — 2.5%) which
  is the soft target; the engine dials below this.
* If the 15-minute rolling abandon rate approaches 3%, the engine automatically
  throttles the ratio toward 1.0 (effectively becoming progressive) until the
  rate drops.
* `predictive_max_wait_s` caps how long an answered lead waits for an agent
  before being released — preventing the worst UX failure mode.

You cannot disable the 3% cap via the API. It is a platform invariant.

## Voice broadcast pattern

A common question: *"Is voice broadcast a fourth dial mode?"* **No.** Voice
broadcast is a **flow-composition pattern** layered on top of either
progressive or predictive. The campaign still uses `dial_mode: "progressive"`
(or `"predictive"`); what differs is the post-answer action.

A voice-broadcast campaign sets:

* `post_answer_action: "run_flow"`
* The flow itself is a small 3-block IVR:
  * `play_audio` — the recorded broadcast message.
  * `collect_digits` — typically `max_digits: 1, timeout_s: 5`, waiting for
    the lead to press **1** to opt in.
  * `connect_agent` — routes confirmed opt-ins to the agent queue.

The dialer UI ships a **"Use voice-broadcast template"** button on the
campaign-create page that pre-fills this flow shape. Because voice broadcast
is just a flow, you can extend it freely: add a second prompt, branch on
multiple digits, send the opt-out to a DNC-update webhook, etc. Everything
other flows can do is available here.