Phone system diagrams | Ringfully

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Most of these are generated from the same modules the site’s own tools run on, so the picture and the arithmetic behind it cannot disagree. Each one says underneath where its numbers came from and, where they came from somebody else, the date the page was read.

To reuse one: credit Ringfully and link to this page. That is the whole licence. The French version of every diagram sits at the same file name with .fr before the extension.

How a call travels

Why a call can connect and still have no sound — Reuse this figure anywhere, including commercially, with credit to Ringfully and a link back to this page. CC BY 4.0.

Published codec bit rate against the real bandwidth of one call on Ethernet. The names promise a ratio of 8.0 to 1 between G.711 and G.729 (8 Kbps); on the wire the ratio is 2.8 to 1. — Reuse this figure anywhere, including commercially, with credit to Ringfully and a link back to this page. CC BY 4.0.

The three one-way delay bands of ITU-T Recommendation G.114, from transparent to unacceptable. — Reuse this figure anywhere, including commercially, with credit to Ringfully and a link back to this page. CC BY 4.0.

Transfer curve of G.711 mu-law against uniform 8-bit coding. G.711 spends 29 of its 128 values on the quietest one percent of the range and 1 on the loudest one percent. — Reuse this figure anywhere, including commercially, with credit to Ringfully and a link back to this page. CC BY 4.0.

Phone numbers

What each part of a number decides — Reuse this figure anywhere, including commercially, with credit to Ringfully and a link back to this page. CC BY 4.0.

Split or overlay: the two ways to add numbers — Reuse this figure anywhere, including commercially, with credit to Ringfully and a link back to this page. CC BY 4.0.

Quebec's four area code families — Reuse this figure anywhere, including commercially, with credit to Ringfully and a link back to this page. CC BY 4.0.

What follows the number, and what stays behind — Reuse this figure anywhere, including commercially, with credit to Ringfully and a link back to this page. CC BY 4.0.

The market

Composition of the 473 million retail voice connections in the United States as of 2025-06-30: 15 million switched access lines, 63 million VoIP subscriptions and 395 million mobile subscriptions. — Reuse this figure anywhere, including commercially, with credit to Ringfully and a link back to this page. CC BY 4.0.

UCaaS, CCaaS, CPaaS: which one you are actually shopping for — Reuse this figure anywhere, including commercially, with credit to Ringfully and a link back to this page. CC BY 4.0.

Lowest published price per seat per month at eight vendors, from 15 to 119 US dollars. — Reuse this figure anywhere, including commercially, with credit to Ringfully and a link back to this page. CC BY 4.0.

Four questions put to 8 competing vendors. None publishes a spending ceiling, included minutes, call-transfer capabilities, or Quebec's privacy law. — Reuse this figure anywhere, including commercially, with credit to Ringfully and a link back to this page. CC BY 4.0.

What it costs, and what it counts

Seat, user, or concurrent call: what you are actually buying — Reuse this figure anywhere, including commercially, with credit to Ringfully and a link back to this page. CC BY 4.0.

Three quantities of different kinds: 258 million Do Not Call registrations, 3.9 billion robocalls in a single month, and 2.6 million complaints in the year. — Reuse this figure anywhere, including commercially, with credit to Ringfully and a link back to this page. CC BY 4.0.

What every phone system asks of an audio file — Reuse this figure anywhere, including commercially, with credit to Ringfully and a link back to this page. CC BY 4.0.

Simultaneous channels needed to keep blocking at or under 1 per cent, by load. One erlang needs 5; four erlangs need 10. — Reuse this figure anywhere, including commercially, with credit to Ringfully and a link back to this page. CC BY 4.0.

Running a phone line

The five metrics, and what one more person does to them — Reuse this figure anywhere, including commercially, with credit to Ringfully and a link back to this page. CC BY 4.0.

Curve of occupancy against call volume at a constant service level. At low volume 3 people run at 36 per cent occupancy; at high volume 56 people run at 89 per cent. — Reuse this figure anywhere, including commercially, with credit to Ringfully and a link back to this page. CC BY 4.0.

Comparison of average speed of answer against the wait actually borne by callers who queue. At 14 people the average is 10 seconds while those who wait hold for 60 seconds. — Reuse this figure anywhere, including commercially, with credit to Ringfully and a link back to this page. CC BY 4.0.

People who must be free in each half hour of an example day. The peak is 20 at 09:30 and the mean is 14.4. — Reuse this figure anywhere, including commercially, with credit to Ringfully and a link back to this page. CC BY 4.0.

Two greetings measured against the 20 second threshold. The second runs about 27 seconds before the first option. — Reuse this figure anywhere, including commercially, with credit to Ringfully and a link back to this page. CC BY 4.0.

The tools behind some of these

Several of the diagrams are drawn by the same code that runs the free tools, where you can put your own numbers in instead of ours.

See the free tools