Basic Telephony Concepts

📖 Introduction

Before configuring Ring2All, it helps to understand basic telephony terms and concepts.

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📞 Key Terms

Extensions

An extension is a phone line inside your organization. Usually a 3-4 digit number like 1001, 1002, etc.

Property	Example
Extension Number	1001
User	John Smith
Device	Desk phone, softphone

DID (Direct Inward Dialing)

A DID is an external phone number that people dial to reach you.

DID	Routes To
+1-555-123-4567	Main IVR
+1-555-123-4568	John's Extension (1001)

SIP Trunk / Gateway

A SIP Trunk (also called Gateway) connects your PBX to the outside world through a VoIP provider like Twilio or Telnyx.

Plaintext

Caller → PSTN → Provider → SIP Trunk → PBX → Extension

IVR (Interactive Voice Response)

An IVR is an automated phone menu:

"Press 1 for Sales"
"Press 2 for Support"
"Press 0 for Operator"

Queue

A Queue holds callers until an agent is available. Used for support lines, sales teams, etc.

Ring Group

A Ring Group rings multiple extensions simultaneously or sequentially until someone answers.

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📊 Call Flow Example

Plaintext

Incoming Call (+1-555-123-4567)
    ↓
Inbound Route (matches DID)
    ↓
Time Condition (is it business hours?)
    ↓
    ├─ Yes → Main IVR
    │           ↓
    │        Press 1 → Sales Queue → Agent answers
    │        Press 2 → Support Queue → Agent answers
    │        Press 0 → Receptionist (ext 1000)
    │
    └─ No → After Hours Announcement → Voicemail

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🔗 SIP Basics

SIP (Session Initiation Protocol)

The protocol that makes VoIP calls work. You'll see these terms:

Term	Meaning
SIP Server	The PBX IP address
SIP Port	Usually 5060 (UDP) or 5061 (TLS)
Username	Extension number
Password	SIP password
Register	Phone connects to server

Registration

When a phone "registers," it tells the PBX:

"I'm extension 1001"
"Reach me at this IP address"

This allows the PBX to route calls to the phone.

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📞 Call Types

Type	Description
Internal	Extension to Extension (1001 → 1002)
Inbound	Outside caller → Extension
Outbound	Extension → Outside number

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💡 Tips

TIP

Test internally first: Make extension-to-extension calls before testing external calls.

TIP

Check registration: Most problems are phone registration issues.

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