# Is anyone here interested in Train Signals and how they work?

**URL:** <https://discourse.nodered.org/t/is-anyone-here-interested-in-train-signals-and-how-they-work/19759>\
**Category:** General\
**Created:** [31 December 2019 01:46 UTC](https://discourse.nodered.org/t/is-anyone-here-interested-in-train-signals-and-how-they-work/19759 "2019-12-31T01:46:51Z")\
**Posts on this page:** 1\
**Showing post:** 21

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**Author:** ![Paul-Reed](https://sea2.discourse-cdn.com/flex026/user_avatar/discourse.nodered.org/paul-reed/32/66906_2.png) [@Paul-Reed](https://discourse.nodered.org/u/Paul-Reed)\
**Post date:** [2 January 2020 23:06 UTC](https://discourse.nodered.org/t/is-anyone-here-interested-in-train-signals-and-how-they-work/19759/21 "2020-01-02T23:06:45Z")

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I just know I'm going to regret asking... but what is FF.  
I know what FNR stands for, I've called it that many times, but what is FF?

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