Aquant Conversational AI — PSTN Integration

Overview What you need Inbound numbers & paths Placing a call Receiving handover Behavior & rules Troubleshooting After the call Changelog

Overview

Each Aquant agent can be reached at one or two published phone numbers. A caller dials the number from any ordinary phone; Aquant answers, routes the call to the AI agent, and the conversation runs in real time. No SIP setup is required on the caller's side — this is standard PSTN dialing.

Three directions

Inbound (caller → Aquant)	A caller dials the agent's published phone number. The AI agent answers and handles the conversation. This is the primary integration.
Handover (Aquant → your PSTN)	If the agent is configured for handover, the AI can transfer a live call to a phone number you host — a human agent, contact center, or on-call line. Warm handover requires the conference-capable number. See Receiving handover.
After the call (you → Aquant REST)	Recording, transcript and an AI-generated summary are produced after the call ends. The summary is retrievable over the ACAI REST API. See After the call.

Not using SIP? This guide covers regular phone numbers only. If your integration originates calls over SIP — softphone, PBX, or SBC — read the SIP Integration guide instead. SIP and PSTN can coexist on the same agent; the path depends on which address the caller dials.

What you need before you start

Published number(s)	One or two E.164 phone numbers issued per agent by your Aquant contact. Which number you publish depends on whether you need one-on-one calls or conference-capable calls (including PSTN handover).
Which path	Whether callers should use the primary agent number or the conference-capable number. This is fixed when the numbers are provisioned and decides whether PSTN handover is available — ask if you aren't sure.
Handover destination	If Aquant will transfer calls to your team, the phone number that should ring — your contact-center queue, helpdesk, or expert line. Configured on the Aquant side per agent.
Transfer-to-human enabled	The agent must have human handover turned on, and a handover destination configured, for the AI to initiate a transfer at all.
Caller allow-list (optional)	If the agent restricts who may call, only numbers registered on the allow-list will connect. The check uses the caller's own phone number (automatic on PSTN).

Where do these come from? Your Aquant administrator provisions phone numbers and handover settings for the agent and shares the numbers you should publish. Ask them to re-issue or reconfigure if anything is missing.

Inbound numbers & call paths

An agent may have a primary number, a conference-capable number, or both. Each number selects a different answer path. Publish the one that matches how callers should reach the agent and whether you need handover to a phone.

DIAL+<country><area><subscriber>

Number format

Field	Example	Description
E.164	+14155550123	Country code, area code, and subscriber number with a leading `+`. Use the full international format your Aquant contact gave you — do not strip the country code.
No special headers	—	Unlike SIP integration, PSTN callers do not send custom headers. The caller's phone number is supplied automatically by the carrier as caller ID.

Two paths, two numbers

When both numbers exist, they are independent entry points to the same agent. A caller must dial the correct one for the behaviour they need.

Path	Number	Answer behaviour	Handover to a phone
Primary	Primary agent number	One-on-one call between the caller and the AI.	Not supported. If the handover destination is a phone number, the transfer is skipped and the caller stays with the AI.
Conference	Conference-capable number	The caller joins a conference; the AI joins the same conference a moment later.	Supported. Aquant dials your handover destination into the live conference — a warm transfer. The caller stays connected throughout.

Dialing the wrong number changes what's possible. Publishing the primary agent number when you need PSTN handover will not work — callers connect fine, but a transfer to a phone never fires. Confirm with your Aquant contact which number to publish before go-live.

Number rotation invalidates the old one. If a number is released and re-provisioned, the previous number stops working immediately. Coordinate any change with your Aquant contact and update every place the old number was published.

Placing a call (inbound)

From the caller's perspective this is an ordinary phone call — dial the published number and wait for the agent to answer. No app, SIP client, or special dialling prefix is required.

What the caller does	Dial the E.164 number you were given, from any phone that can reach the number's country and carrier routing.
What happens on answer	The AI agent greets the caller and handles the conversation in natural language. On the conference path there may be a brief pause while the conference is set up before the AI speaks.
Caller ID recorded	The caller's phone number (as presented by their carrier) is stored on the call record and shown in call history. No extra identity field is required on PSTN.
Hanging up	Either party hanging up ends the call normally. If recording and analysis are enabled, processing begins after disconnect.

When the call is not accepted

Most rejection reasons are delivered as a connected call that plays a short spoken message and then hangs up — not as a busy signal or "number disconnected" tone. If monitoring from your side, look for very short answered calls rather than failed dial attempts.

Situation	What the caller hears
Unknown or inactive agent, or wrong number	"Sorry, the voice agent is not available."
Caller not on the allow-list	The agent's configured unauthorized-caller notice (custom text per agent).
Organization deactivated or out of credit	"Sorry, this service is temporarily unavailable. Please try again later."

Treat credit and account issues as retryable. The unavailable message for billing or account standing is not a fault in your dialling setup. Remediation is on the Aquant account side; retry once service is restored.

Receiving handover (Aquant → your PSTN)

When the AI decides to transfer — because the caller asked for a human, because a workflow rule fired, or because the conversation reached its turn limit — Aquant can dial your handover destination and bridge the caller through. On PSTN this is always a warm transfer: the caller stays on the line, Aquant adds your destination to the same conference, and the AI may brief your agent before stepping back.

Conference path only. PSTN handover requires callers to have reached the agent via the conference-capable number. Calls on the primary one-on-one path cannot be forwarded to a phone — only to a SIP destination, which is covered in the SIP Integration guide.

Destination	A phone number you host — contact-center queue, helpdesk, mobile, or any PSTN endpoint that can receive an inbound call. Configured by your Aquant contact as the handover destination for the agent.
What you receive	An inbound phone call from Aquant. Answer it as you would any transferred customer call; the original caller is already connected in the background conference.
Handover briefing	Once your agent answers, the AI can speak a short summary of the conversation so far. This can be disabled per agent for a silent join.
Caller ID you will see	For callers who dialled in over PSTN, Aquant forwards the original caller's number where the carrier and local regulations permit. If forwarding is not permitted, or the original leg was not a dialable phone number, you will see the agent's own number instead. Do not assume the displayed number is always the end customer.
Call reference on phone legs	There is no call-reference header on a phone handover — that mechanism exists on SIP legs only. See the SIP Integration guide if you need to correlate a transferred SIP leg back to the Aquant call record.
Timing	The AI says a closing line first; your phone typically rings about ten seconds later. Expect a short gap between "transferring you now" and your destination ringing.

What to prepare on your side

Answer the handover line	Your destination must accept inbound calls from Aquant's outbound dialling. If you use an IVR or queue, route the Aquant caller ID (or the agent number, if forwarding was blocked) to the right team.
Share the destination number	Give your Aquant contact the E.164 number that should ring, and confirm it is scoped to the same project as the agent.
Confirm conference publishing	Make sure callers are dialling the conference-capable number, not the primary agent number, if you depend on phone handover.

Setup is coordinated. Handover destination, transfer-to-human enablement, and silent-vs-briefing behaviour are all configured on the Aquant side. Share your requirements with your Aquant contact before testing.

Behavior & rules

Routing	Aquant selects the agent from the called number — the E.164 value the caller dialled. Each number maps to exactly one agent.
Agent must be active	The target agent must be active. Otherwise the call is answered and an unavailable announcement is played.
Numbers are sensitive	Published numbers are direct entry points to the agent. Treat them like credentials — anyone who has the number can call unless caller authentication is enforced.
Caller allow-list	When enabled, only registered caller phone numbers connect. On PSTN the check uses the caller's automatic caller ID — no extra setup on the caller's phone.
Account standing	Calls may be rejected when the owning organization is deactivated or has exhausted its credit: the caller hears a temporarily-unavailable message and the call ends.
Recording & analysis	When enabled on the agent, the call is recorded and transcribed, and a summary is generated after it ends. See After the call.
When the AI transfers	Transfer can be triggered by the caller asking for a human, by configured workflow rules, or when the conversation reaches the agent's session turn limit. All require transfer-to-human to be enabled and a resolvable handover destination.

Troubleshooting

Symptom	Likely cause	What to check
Caller hears "not available" immediately	Wrong number, inactive agent, or number no longer provisioned	Confirm the exact E.164 with your Aquant contact. Verify the agent is active and the number has not been rotated.
Caller hears unauthorized notice	Caller allow-list is on and this phone number is not registered	Add the caller's number to the allow-list, or disable caller authentication for testing.
AI says it is transferring but your phone never rings	Caller used the primary one-on-one number, or no handover destination is configured	Publish the conference-capable number for PSTN handover. Confirm transfer-to-human is enabled and a destination phone number is configured on the Aquant side.
Handover rings but caller ID is unexpected	Carrier or regulatory limits blocked forwarding the original caller's number	Normal on some routes — you may see the agent's number instead. Do not rely on caller ID alone to identify the customer on the handover leg.
Very short answered calls with a spoken message	Application-level rejection (inactive, unauthorized, account standing)	These are not carrier busy signals. Check call history in Aquant and the rejection table in Placing a call.
One-way audio or no audio after connect	Carrier or network issue on the PSTN path	Escalate to your Aquant contact with the call time, both phone numbers, and whether the issue is on the inbound leg, the handover leg, or both.

After the call

When the agent has recording and analysis enabled, Aquant transcribes the call and generates a summary once it ends. The summary is available over the ACAI REST API, so a PSTN integration can pull conversation outcomes back into your CRM or ticketing system without screen-scraping the console.

GEThttps://acai-api.aquant.ai/acai/call/{call_record_id}/summary

Authenticate first

Exchange your ACAI API credentials for a short-lived bearer token (valid one hour, refreshed on use), then call the summary endpoint with it. The token is bound to one agent, and the endpoint only returns calls handled by that agent.

# 1 — get a session token
POST https://acai-api.aquant.ai/acai/auth
{ "api_key": "...", "api_secret": "...",
  "agent_id": "...", "sender_id": "your-system" }

# 2 — read the summary
GET https://acai-api.aquant.ai/acai/call/{call_record_id}/summary
Authorization: Bearer <token>

Response

{
  "call_record_id": "6cbd7ac0-33ab-4790-9c3c-bdfc64a4e079",
  "status": "Ready",
  "summary": "The caller reached out for assistance regarding..."
}

Status	Meaning	What to do
`Ready`	Summary is available in `summary`.	Consume it.
`Pending`	Analysis is still running, or the text is mid-write.	Poll again shortly.
`Failed`	Analysis ran and failed.	Stop polling; no summary will arrive.
`Unavailable`	Analysis was never requested for this call — recording or analysis is off on the agent.	Stop polling; enable the feature on the agent if you need summaries.

Because the summary is asynchronous, always branch on status. A null summary on its own doesn't tell you whether to wait or give up. Calls belonging to any other agent return 404, so use the token for the agent that handled the call. The endpoint is rate limited per token; poll at a few seconds' interval rather than in a tight loop.

The call record id is visible in Aquant call history. On SIP handovers it can also be carried in a call-reference header — see the SIP Integration guide for that path. PSTN handovers do not deliver it on the phone leg.

Changelog

What changed in this revision of the reference.

Date	Change
19 Aug 2026	Initial PSTN reference. Covers inbound dialling on primary and conference-capable numbers, warm PSTN handover (conference path only), caller allow-list behaviour on PSTN, application-level rejection messages, and the shared post-call summary API. Cross-links to the SIP Integration guide for SIP-specific topics.