Branch phones register and call through the box, with audio compressed for the trip.
Phones at a branch now register and place calls through the box as though they sat at the main office.
Everything just works
Registering, calls in both directions, hold, transfer, the voicemail light, busy lights. None of it needed a change to the main system. As far as it can tell, the branch phones are ordinary phones behind an ordinary router.
The box makes no decisions and holds no passwords. A phone signs in to the main system through it, and the box only carries the conversation.
Smaller on the wire
Inside the branch, a phone speaks to the box in an ordinary desk phone codec. Across the internet, the box compresses it.
- A classic phone call
- Through the box
About a quarter. And when nobody is talking, the box sends next to nothing.
Smoothing the bumps
The internet loses packets and delivers others late. The box holds a very short buffer of audio, starting at 40 milliseconds, and plays it to the phone on a steady beat. Each packet carries a spare copy of the one before, so a lost packet can usually be rebuilt exactly.
If the line gets worse, the box lowers its bitrate to fit. When the line recovers, it raises it again.
How much can a box carry?
We ran the box's real audio code at full load on our test desktop:
| Calls at once | Processor used |
|---|---|
| 400 | 3 of 10 cores |
| 800 | 5.5 of 10 cores |
Every frame was played and nothing was lost in the link. A branch box is a smaller computer than our test machine, and a branch is a great deal smaller than 400 calls.
Next
What happens when the internet goes out.