School of Specs CT1 — the group that writes what your…Quick start

TS 24.501 · version 20.0.0 · 1340 clauses · Quick start · 15 minutes

CT1 — the group that writes what your phone says

Before your phone carries a single byte of anybody's data it has a conversation with the network, in named messages with fixed contents that nobody ever sees. Somebody had to decide what those messages are called, what goes in each one and what happens when one arrives damaged — and that somebody is a committee, working group 1 of 3GPP's CT group. This quick start says what the group is, what it produces, how one small change gets into one of its documents, and how to read the record yourself. Every number in it was read out of the 3GPP data held on this machine on 2026-08-04, and every claim links to what it came from.

Start at chapter 1 Sit the final test Look at the document first

This course was written against TS 24.501 version 20.0.0, and built from a source register generated 2026-08-04.

Same subject, different depth: overview · in depth

The document, all of it

One block per clause of TS 24.501, in the order they appear, sized by how much text the clause holds. Lit blocks are taught in this course.

Open the whole of TS 24.501 as a page

The chapters

Part 1 What CT1 is and what it makes

  1. 1 Who writes the words your phone actually sends What CT1 is, who sits in the room, and why an agreement like this one has to be written by a committee rather than by a company. 3 min
  2. 2 What the group produces, and what one of its documents looks like The 229 active CT1 specifications, and a guided look at the one it changes most — TS 24.501, the protocol between your phone and the 5G core. 4 min

Part 2 How the work moves, and how to follow it

  1. 3 How something gets into a specification The change request, the meeting that decides it and the version number that comes out — with the real numbers from one meeting, C1-161. 4 min
  2. 4 How to look at CT1's work yourself, and what the record does not say Where the documents, meetings, office holders and specifications are published, how fresh the data is, and the questions this record cannot answer. 4 min

Testing yourself

Every question at once

16 questions, chapter by chapter, on one page — for revision after you have read the course.

Open all the questions

The final test

10 questions drawn across the whole course, marked at the end. 60 per cent to pass, and every miss says which chapter to go back to.

Sit the final test

What this course is built on

Chapters
4
Words written for you
2,850
Clauses covered
12 of 1340
Figures from the document
45
Abbreviations
201
Published versions
69
Checked sources
354
Sources this course cites
61

The document · Words · History · Documents around it · Every source