Fax Technology

Connected clusters

• Printing History
• Document Workflows
• Mobile Printing

In the archive

• History
• Glossary
• Fax

Pages in this cluster

• Toner
• The History of Desktop Publishing
• Printing in the 1980s
• How Impact Printing Worked
• Analog Fax vs Digital Fax
• Print Servers in Large Offices

Planned coverage

• The T.30 Fax Protocol: How a Fax Call Is Negotiated — Walks through the five phases of a T.30 session (call setup, pre-message negotiation, message transmission, post-message, disconnect) using standard HDLC frame names.
• T.4: How Group 3 Fax Encodes a Page — Explains the ITU-T T.4 recommendation for scanning, resolution options, and one-dimensional/two-dimensional line coding.
• T.6 and MMR: Two-Dimensional Fax Compression — Describes Modified Modified READ coding used by Group 4 and optionally Group 3, and how it compresses relative to earlier schemes.
• Modified Huffman Coding in Fax Transmission — How run-length Modified Huffman (MH) compresses black-and-white scan lines, the baseline T.4 one-dimensional mode.
• Fax Groups 1 to 4: The ITU-T Classification Explained — Neutral comparison of the Group 1/2/3/4 designations, what distinguishes analog from digital groups, without invented adoption figures.
• Error Correction Mode (ECM) in Group 3 Fax — How ECM frames and retransmission improve reliability over noisy phone lines, as defined in T.30 annexes.
• Fax Modem Modulation: V.27ter, V.29 and V.17 — Explains the ITU-T modulation standards that carry fax image data and their nominal signaling roles during a call.
• Super G3 Fax and the V.34 Modulation Standard — What Super G3 refers to, how V.34 modulation applies to fax, and the T.30 fast-negotiation procedure it uses.
• CNG and CED: The Handshake Tones of a Fax Call — Defines the calling (CNG) and called-station (CED) tones and their role in distinguishing fax from voice calls.
• T.38: Real-Time Fax over IP Networks — Explains the T.38 recommendation for relaying fax across packet networks and why real-time faxing differs from voice over IP.
• T.37: Store-and-Forward Internet Fax — Describes the T.37 email-based fax model using MIME and TIFF-F profiles, contrasted with real-time T.38.
• Fax Pass-Through Over G.711 Voice Codecs — How fax can traverse VoIP as a G.711 audio stream, and why packet loss and echo cancellation complicate it.
• Fax Resolution: Standard, Fine and Superfine — Explains the horizontal and vertical resolution options defined for Group 3 fax and how they affect image detail.
• How Fax Travels Over the PSTN — Grounds fax in the analog public switched telephone network: audio-band signaling, dialing, and call setup.
• Fax Transmission Reports and Confirmation Pages — Explains what a transmission confirmation report records and how T.30 post-message signals underpin it.
• Fax Header Lines: What TSI and the Printed Header Convey — Describes the transmitting subscriber identification frame and the human-readable header commonly printed atop pages.
• Radiofax and Marine Weather Facsimile — Covers HF radio facsimile used for weather charts, a distinct analog facsimile lineage from telephone fax.
• From CCITT to ITU-T: Who Standardizes Fax — Traces the standards body that authored the T-series recommendations and its renaming, without invented milestone dates.
• Internet Fax and Email-to-Fax Gateways — Explains how gateway services bridge email/web submissions to the fax network, in neutral educational terms.
• Baud and Bit Rate in Fax Transmission — Defines baud versus bit rate as they apply to fax modem signaling to clear up a common conflation.
• HDLC Framing in Fax Signaling — Short glossary entry on the HDLC frame structure T.30 uses for its control messages.
• Why Fax Can Fail Over VoIP Lines — Explains packet loss, jitter, and codec transcoding as the technical reasons analog fax struggles on VoIP, motivating T.38.