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Qzentra

Case fileAI Agents & Voice AI

AI Voice Receptionist and Outbound Sales Agents

Two voice systems: an AI receptionist that answers calls and books appointments into Google Calendar, and outbound AI calling agents for sales. Both answer from a knowledge base and hand urgent calls they cannot answer to a person.

Appointments booked into Google Calendar during the call

  • Voice AI
  • Google Calendar
  • knowledge base
  • LLM APIs
  • telephony

Layer coverage

  1. Data: worked in this layer
  2. Infrastructure: not part of this system
  3. APIs: worked in this layer
  4. AI: worked in this layer
  5. Automation: worked in this layer
  6. Application: worked in this layer
Enters through
AI Agents & Voice AI
System
Telephony-connected voice agents, inbound and outbound
Also demonstrates
AI Systems & Automation

The challenge

Two phone workloads depended on people being available. Inbound callers needed answers and appointments, and outbound sales depended on someone working through prospects one call at a time.

Both needed an AI on the phone that answered from what the business actually knows, acted during the call, and recognised when a person had to take over.

What made it non-trivial

  • Latency: recognition, reasoning, and synthesis have to fit inside a natural conversational pause
  • Appointments have to land in Google Calendar during the call, not in a follow-up
  • Answers must come from the saved knowledge base, and the agent must recognise when it has none
  • An urgent call the agent cannot answer must reach a person rather than a dead end

What Qzentra engineered

Qzentra built an AI receptionist that answers inbound calls, responds from the business’s knowledge base, and books appointments directly into Google Calendar while the caller is on the line.

Alongside it, Qzentra built outbound AI calling agents that place sales calls to prospects, on the same foundation: telephony, real-time speech recognition, an LLM for conversation logic, and speech synthesis.

Both follow one escalation rule. When there is no proper response saved in the knowledge base and the call seems urgent, the call is handed to a person.

What Qzentra was responsible for

  • Voice agent architecture, inbound and outbound
  • AI receptionist conversation design
  • Outbound sales calling agents
  • Knowledge base for grounded answers
  • Google Calendar appointment booking
  • Escalation and human handoff

How the system works

The loop a single call travels. Recognition, reasoning, and synthesis have to complete inside a conversational pause; bookings land in the business's own Google Calendar.

  1. Inbound or outbound call

    APIs

    The receptionist answers incoming calls; the sales agents place calls to prospects. Both run on a telephony layer.

  2. Speech recognition

    AI

    The caller’s speech is transcribed in real time.

  3. Knowledge base

    Data

    Answers come from the knowledge base saved for the business, not from the model’s general memory.

  4. LLM conversation logic

    AI

    An LLM decides what to say next: answer the question, book the appointment, or move the sales conversation forward.

  5. Google Calendar booking

    Automation

    The receptionist books the appointment into Google Calendar while the caller is still on the line.

  6. Speech synthesis

    AI

    The response is spoken back to the caller.

  7. Handoff to a person

    Application

    When the knowledge base has no proper response and the call seems urgent, the call is handed to a person.

The call drawn as a system.Speech crosses telephony into the agent, which answers from the knowledge base beneath it. The call is booked into the calendar, answered and done, or handed to a person when the matter is urgent and unsaved.

Engineering decisions

  1. Answers from the knowledge base

    The agents respond from what is saved in the knowledge base rather than improvising, so a gap in that knowledge is detectable instead of hidden behind a guess.

  2. Booking inside the call

    The receptionist writes the appointment to Google Calendar while the caller is still on the line, so the booking is settled in the conversation rather than chased afterwards.

  3. Escalate on a gap plus urgency

    A call goes to a person when the knowledge base has no proper response and the matter seems urgent. Routine calls stay with the agent; urgent unknowns do not wait.

  4. Telephony as the boundary

    The telephony layer carries the call; the conversation logic, knowledge base, and calendar integration sit behind it and can change without changing the number the caller dials.

What was achieved

  • Inbound calls answered and appointments booked into Google Calendar by the AI receptionist
  • Outbound sales calls placed and held by AI calling agents
  • Answers grounded in the business’s saved knowledge base
  • Urgent calls outside the knowledge base handed to a person

Technology, after the architecture

Named last, with the role each played. The capabilities are what the project demonstrates beyond its primary service.

  • Twilio, Vapi, Retell AITelephony and voice agent platforms
  • DeepgramSpeech recognition
  • ElevenLabsSpeech synthesis
  • LLM APIsConversation logic
  • Knowledge baseSaved answers the agents respond from
  • Google CalendarAppointment booking
  • n8n and webhooksWorkflow and API integration

Capabilities demonstrated

  • voice AI architecture
  • telephony integration
  • speech recognition and synthesis
  • knowledge-base grounding
  • calendar integration
  • human handoff

Discuss a project

Have calls that a person is answering when a system could?

Tell us the calls you take and make, the calendar or systems the agent must act in, and when a person should take over. That is the specification to start from.