> ## Documentation Index > Fetch the complete documentation index at: https://docs.lehar.ai/llms.txt > Use this file to discover all available pages before exploring further. # Channels > The ways an agent can reach a user: web voice, outbound phone, and WhatsApp. Lehar agents talk to users over three channels. The same agent configuration (prompt, variables, knowledge base) can drive any of them. ## Web voice A browser participant connects to a media room and talks to the agent over WebRTC. You create a [session](/concepts/sessions), then connect the returned `participant_token` with a voice client. Best for in-product voice assistants and click-to-talk experiences. ## Outbound phone The agent dials a recipient over SIP and runs the same conversation loop. Create a session with `call_type: "outbound_phone"` and a `phone_number`, or run a **`voice`** [campaign](/concepts/campaigns) to place many calls. Requires an outbound SIP trunk on the deployment. ## WhatsApp Text conversations delivered through WhatsApp (via the messaging provider). Two campaign types use this channel: * **`whatsapp`** — the agent holds a text conversation with the recipient. * **`whatsapp_voice`** — sends an approved template, waits for a reply, decides whether the recipient wants a call, and escalates to the outbound voice path when they do. WhatsApp sends are governed by the **24-hour customer-service window** (free-form messages are only allowed within 24h of the last inbound message; outside it, only approved templates). See the [WhatsApp guide](/guides/whatsapp). ## At a glance | Channel | Transport | Trigger | | -------------- | ------------------ | -------------------------------------------------------------------- | | Web voice | WebRTC | `POST /sessions` (`call_type: web`) | | Outbound phone | SIP | `POST /sessions` (`call_type: outbound_phone`) or a `voice` campaign | | WhatsApp | Messaging provider | `whatsapp` / `whatsapp_voice` campaign | Web and phone voice calls. Templates, windows, and escalation.