Black channel
The principle that a safety protocol treats everything between two safety devices, including switches, routers, and radios, as unproven, and detects transmission errors end to end itself.
The network analogy
The end-to-end argument applied to safety: the endpoints add their own sequence checks, timers, and CRCs instead of trusting any link in between.
Why it matters for wireless
Black channel is why Wi-Fi can carry safety traffic without being safety certified. It does not make Wi-Fi's delays harmless: the endpoints still check timeliness, and a link that is too slow trips the safety function.
The black channel
The safety protocol trusts only its two endpoints. Everything between them is treated as unproven, including the radio.
Schematic, not to scale
IEC 61784-3 defines a black channel as a communication system containing elements without evidence of design or validation to IEC 61508. Ethernet's own error detection may not satisfy any part of the safety function; the endpoints carry it.
Sources: IEC 61784-3, ODVA on wireless functional safety, and the PROFIsafe system description.
IEC 61784-3 defines a black channel as a communication system containing one or more elements without evidence of design or validation according to IEC 615081. ODVA puts it plainly: Ethernet’s own error detection may not be used to satisfy any part of the safety function.
The checks live in the endpoints instead. PROFIsafe uses consecutive numbering, a watchdog, an F-address, and a CRC; CIP Safety uses time stamps with time expectation, unique device identifiers, and integrity checks. Timeliness is one of those checks, which is why the radio still matters.
About this page
Built from 3 sources: 1 standards body or lab and 2 protocol owners and alliances. Researched and drafted with AI assistance, then reviewed and approved by Ben Rutter on . How pages are made
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Cite this page
Plain
Ben Rutter. "Black channel." OT Wireless, published October 5, 2026. https://otwireless.com/glossary/black-channel/
APA 7
Rutter, B. (2026, October 5). Black channel. OT Wireless. https://otwireless.com/glossary/black-channel/
BibTeX
@misc{rutter2026blackchannel,
author = {Rutter, Ben},
title = {{Black channel}},
year = {2026},
howpublished = {\url{https://otwireless.com/glossary/black-channel/}},
organization = {OT Wireless},
}