Predictive vs Progressive vs Preview Dialer

The dialer mode you choose determines three things simultaneously: how many conversations your agents have per hour, how much compliance risk your campaign carries, and how much revenue each answered call generates. Most operators default to predictive because it sounds like the most aggressive option. Sometimes it is the right choice. Sometimes progressive or preview would generate more revenue despite lower dial volume, because the conversations are better and the compliance exposure is lower.

This guide compares the three primary dialer modes from an operational perspective. SIPNEX provides SIP trunks for all three modes — the carrier requirements are the same regardless of which mode you run. What changes is how aggressively your system uses the trunk capacity, and what tradeoffs you accept.

Predictive dialing

Predictive dialing uses algorithms to dial multiple numbers per available agent, predicting when an agent will become free based on real-time answer rates and call durations. The dialer places 3 to 5 calls (or more) per available agent simultaneously. When a call is answered, it is connected to the next available agent. When calls are not answered, they are disposed and new calls are launched.

Agent utilization: 85 to 95 percent talk time. Agents spend the vast majority of their shift in conversation. Idle time between calls is measured in seconds, not minutes.

Compliance risk: The highest of the three modes. When the algorithm over-predicts (more calls answered than agents available), calls are answered by live humans with no agent to take them. These are abandoned calls. The FCC limits the abandon rate to 3 percent measured over 30 days per campaign. Exceeding this threshold is a TCPA violation at $500-$1,500 per abandoned call. VICIdial’s adaptive algorithm can target a specific drop percentage, but statistical variance means even well-configured campaigns occasionally spike above target.

Conversion quality: Variable. Agents connect to live answers with no preparation — they do not see the lead record until the call connects. The first 3 to 5 seconds of every call are the agent orienting themselves to who they are talking to. For simple, scripted interactions (collections right-party contact, appointment confirmation, survey introduction), this cold-connect approach works fine. For complex sales or consultative conversations, the lack of preparation can hurt conversion rates.

Carrier requirements: Highest concurrent channel demand. 50 agents at 4:1 ratio = 200 concurrent SIP sessions. Requires unlimited channels, low PDD, and A-level attestation for maximum answer rate.

Best for: High-volume B2C campaigns with large lead lists, collections (right-party contact), appointment setting, political polling, any campaign where dial volume drives results and leads are relatively interchangeable.

Progressive dialing

Progressive dialing (also called power dialing) places exactly one call per available agent. When an agent finishes a call and enters available status, the dialer immediately places one call for that agent and waits for the result — answered, voicemail, no answer, busy, or disconnected. Only one call is active per agent at any time.

Agent utilization: 50 to 70 percent talk time. Agents wait through each ring cycle (typically 15 to 30 seconds per attempt) before either connecting to a live answer or moving to the next number. At a 20 percent answer rate, roughly 4 out of 5 dial cycles result in waiting through rings without a conversation.

Compliance risk: Minimal for abandon rate. Since only one call is placed per agent, there is never a situation where a call is answered with no agent available — the agent is always waiting for that specific call. Abandon rate is effectively zero from the dialer mode itself (abandoned calls can still occur if the agent disconnects or the system glitches, but these are operational errors, not algorithmic over-dialing). This makes progressive dialing the safest mode for TCPA compliance.

Conversion quality: Better than predictive for complex conversations. The agent has a brief window during the ring cycle to glance at the lead record (if displayed), but the primary advantage is psychological — agents are less rushed than in predictive mode. They know the next call is specifically theirs, not a random connection from a pool. This subtle difference improves opening delivery and engagement on calls where the first 10 seconds determine the outcome.

Carrier requirements: Lower concurrent channel demand than predictive. 50 agents = 50 concurrent sessions. Still benefits from unlimited channels (no risk of throttling), low PDD, and A-level attestation.

Best for: Regulated industries (healthcare outreach, financial services), compliance-sensitive campaigns where even a small abandon rate is unacceptable, mid-value leads where conversation quality justifies lower volume, and any campaign where the regulatory environment makes predictive dialing risky (Florida campaigns, campaigns to cell phones where consent status is uncertain).

Preview dialing

Preview dialing shows the agent the complete lead record before any call is placed. The agent reviews the information — name, account history, previous interactions, notes, custom fields — and decides whether to dial or skip. When the agent clicks “dial,” the system places the call. The agent is fully prepared before the conversation begins.

Agent utilization: 30 to 50 percent talk time. Every call includes a review period (10 to 60 seconds depending on record complexity) plus the ring cycle. The total time from one conversation to the next can be 30 to 90 seconds even if every call is answered. This is the lowest efficiency mode by a significant margin.

Compliance risk: Lowest of all three modes. No algorithmic dialing means no abandon rate risk. The agent manually initiates each call, which may strengthen the argument that the system is not an ATDS under post-Duguid analysis (though this legal question is not settled). Manual initiation also allows agents to screen for DNC flags, note-based exclusions, and calling hour compliance before dialing.

Conversion quality: Highest. The agent knows who they are calling, why, and what the history looks like before the first word is spoken. “Hi Mrs. Johnson, I see you spoke with my colleague Sarah last Tuesday about your renewal — I wanted to follow up on the questions you had about the coverage options” is a fundamentally different opening than “Hi, this is Mike from ABC Insurance, how are you today?” The preparation eliminates the cold-connect problem entirely and enables personalized conversations from the first second.

Carrier requirements: Lowest concurrent channel demand. 50 agents in preview mode = approximately 30 to 40 concurrent sessions (not all agents are on calls simultaneously). Standard SIP trunk capacity is more than sufficient. A-level attestation still matters — the recipient still sees your caller ID regardless of how the call was initiated.

Best for: High-value B2B sales, insurance renewals, complex financial consultations, legal intake, any campaign where the average deal value is high enough that the lower dial volume is justified by higher per-call conversion, and campaigns where personalization is the primary differentiator.

How to choose: the decision framework

The choice between modes is not about which is “better” — it is about which tradeoff profile matches your campaign.

Choose predictive when: lead value is low to medium, your list is large (10,000+ records), the conversation is scripted and simple, your compliance infrastructure is solid (consent documented, DNC scrubbed, calling hours enforced), you have technical staff who can monitor and adjust the adaptive algorithm, and volume is the primary driver of revenue.

Choose progressive when: lead value is medium, your list is moderate (1,000-10,000 records), compliance risk is elevated (regulated industry, uncertain consent status, Florida or other strict-state campaigns), you want the efficiency benefits of automation without the abandon rate risk of predictive, or you are scaling up a new campaign and want to test performance before switching to predictive.

Choose preview when: lead value is high ($500+ per conversion), your list is curated (under 1,000 records), personalization drives conversion (the agent’s preparation before the call directly impacts outcome), the relationship is ongoing (renewals, account management, consultative sales), or regulatory requirements make automated dialing risky.

Use multiple modes. The most sophisticated operations run different modes on different campaigns simultaneously. VICIdial supports all three modes and allows switching per campaign without changing the underlying trunk configuration. Your SIPNEX SIP trunk supports all three modes identically — the trunk does not know or care which dialer mode is generating the SIP INVITEs.

The carrier is the same regardless of mode

Regardless of which dialer mode you choose, the carrier requirements are consistent:

A-level STIR/SHAKEN attestation improves answer rates in all three modes. A call that goes unanswered because of “Scam Likely” is a wasted dial cycle whether it was initiated by an algorithm or by an agent clicking a button.

Unlimited concurrent channels matter most for predictive but provide headroom for progressive and preview operations that may run multiple simultaneous campaigns.

Low PDD matters most for predictive (where PDD variability breaks the algorithm) but improves the agent experience in all modes — nobody likes waiting 8 seconds for a ring to start.

Carrier-level call recording supports compliance documentation for all modes.

SIPNEX provides the same trunk for all three modes. The configuration is on your PBX side, not ours.

Frequently asked questions

What is the difference between predictive and progressive dialing?

Predictive dialing uses algorithms to dial multiple numbers per available agent simultaneously, predicting when agents will be free. It maximizes agent talk time (85-95%) but creates abandon rate risk when the algorithm over-dials. Progressive dialing places exactly one call per available agent — when an agent becomes free, one call is placed. Agent talk time is lower (50-70%) but abandon rate risk is effectively zero. Choose predictive for high-volume campaigns where efficiency drives revenue. Choose progressive for compliance-sensitive campaigns where abandon rate risk is unacceptable.

When should I use preview dialing instead of predictive?

Use preview dialing when: the average deal value is high enough that fewer but better conversations generate more revenue than high-volume scripted calls (typically $500+ per conversion), the lead relationship is ongoing and personalization matters (renewals, account management), the lead list is curated and small (under 1,000 records), or regulatory constraints make automated dialing risky. Preview dialing gives agents time to review the lead record before calling, producing personalized conversations from the first second. The tradeoff is significantly lower dial volume — 30-50% agent talk time versus 85-95% on predictive.

Can I switch between dialer modes on the same campaign?

In VICIdial, yes. You can change the dialer mode at the campaign level without modifying your SIP trunk configuration. Switch from predictive to progressive mid-campaign if abandon rates spike. Switch from preview to progressive if conversion data shows that agent preparation is not improving outcomes. The SIP trunk handles all three modes identically — the mode is a dialer-side configuration, not a carrier-side one. Some commercial contact center platforms also support mode switching, though the flexibility varies by vendor.

Does the dialer mode affect STIR/SHAKEN attestation?

No. STIR/SHAKEN attestation is applied by the carrier at the SIP trunk level, not by the dialer. Whether your system sends a SIP INVITE because an algorithm triggered it (predictive), because a 1:1 rule triggered it (progressive), or because an agent clicked a button (preview), the carrier signs the call the same way. A-level attestation is based on your number authorization status with the carrier, not on how the call was initiated. All three modes benefit equally from A-level attestation on SIPNEX.

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SIPNEX provides SIP trunks that support all three dialer modes with A-level STIR/SHAKEN attestation, unlimited channels, and low PDD. The mode is your choice. The trunk is ours. Request a dialer-grade trunk or see our rates.