External service
The provider gives the business one or more public numbers and a defined number of simultaneous call channels.
Internal users
Extensions identify people, desks, departments or softphones inside the system. You may have many extensions but fewer concurrent external calls.
Size around peak time
Review the busiest hour, missed calls and transfer patterns. The right channel count comes from demand, not employee count alone.
Project checklist
- Separate public numbers from internal extensions in the quotation
- Confirm simultaneous inbound and outbound calls
- Document the IVR and overflow destination
Practical takeaways
- Define the operating requirement before choosing products
- Document interfaces, failure behaviour and ownership
- Test the completed system and keep records for support
