What a SIP trunk is
It is a voice connection over the internet between the company’s phone system (PBX) and a provider that links it to the public phone network. It replaces physical lines: instead of one cable per line, capacity is measured in channels.
Each channel carries one simultaneous call. If 40 agents are talking at the same time at peak hour, the trunk needs at least 40 channels available.
Trunk, numbers and PBX: how they fit
- Numbers are the lines your customers dial and the ones they see when you call.
- The SIP trunk carries calls between those numbers and your phone system.
- The PBX routes calls to extensions, queues and agents. When it is hosted, the provider runs it and you do not set up your own infrastructure.
Signs you need one
- The calling team is growing and traditional lines no longer keep up.
- You operate across several sites or with remote agents.
- The phone bill is under review and you want to pay for the capacity you use.
- You need numbers in several cities without opening an office in each.
What to check before you sign
- How many simultaneous channels you need at peak, with headroom.
- Whether there is a backup trunk when the main one fails.
- What happens to your current numbers and how long moving them takes.
- How call quality is measured and who answers when it drops.
- Whether numbers are checked before dialing, so attempts are not wasted on numbers that do not work.
Questions
How many channels do I need?
As many as your simultaneous calls at peak hour, plus headroom for unexpected peaks.
Can I keep my current numbers?
It depends on your current carrier and the type of number. Check it before you plan the migration.
Do I need to buy equipment?
Not if the PBX is hosted: the provider runs it and agents use IP phones or apps on their computer or phone.
Talk about Groundline
Tell us what numbers, trunks or switch you need. The brief goes straight to the lab.