# Event on change of digital signal status

**URL:** <https://discourse.nodered.org/t/event-on-change-of-digital-signal-status/23926>\
**Category:** General\
**Created:** [30 March 2020 21:49 UTC](https://discourse.nodered.org/t/event-on-change-of-digital-signal-status/23926 "2020-03-30T21:49:52Z")\
**Posts on this page:** 4\
**Page:** 1

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**Author:** ![rromele](https://sea2.discourse-cdn.com/flex026/user_avatar/discourse.nodered.org/rromele/32/18431_2.png) [@rromele](https://discourse.nodered.org/u/rromele)\
**Post date:** [30 March 2020 21:49 UTC](https://discourse.nodered.org/t/event-on-change-of-digital-signal-status/23926/1 "2020-03-30T21:49:53Z")

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Hi,

a digital signal has a polling reading of 20sec if its value is TRUE every 20sec sends an email, how can I send the email only once when the signal status changes from False to True?

Thanks ![000](https://us1.discourse-cdn.com/flex026/uploads/nodered/original/3X/7/6/7639c17924f89542fa604647b5e3de60534f4834.jpeg)

[000.json](https://discourse.nodered.org/uploads/short-url/yBmUucVSOZgucO1Qe71jr4v7jNk.json) (1.3 KB)

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**Author:** ![dceejay](https://sea2.discourse-cdn.com/flex026/user_avatar/discourse.nodered.org/dceejay/32/38_2.png) [@dceejay](https://discourse.nodered.org/u/dceejay)\
**Post date:** [30 March 2020 22:02 UTC](https://discourse.nodered.org/t/event-on-change-of-digital-signal-status/23926/2 "2020-03-30T22:02:16Z")

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look at the RBE node

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**Author:** ![rromele](https://sea2.discourse-cdn.com/flex026/user_avatar/discourse.nodered.org/rromele/32/18431_2.png) [@rromele](https://discourse.nodered.org/u/rromele)\
**Post date:** [30 March 2020 22:51 UTC](https://discourse.nodered.org/t/event-on-change-of-digital-signal-status/23926/3 "2020-03-30T22:51:45Z")

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perfect!!!!  
thank you very much for helping.  
R.

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**Author:** ![system](https://us1.discourse-cdn.com/flex026/uploads/nodered/original/1X/d073cd938eafa2e558d7c2cd59003b3ef4963033.png) [@system](https://discourse.nodered.org/u/system)\
**Post date:** [13 April 2020 22:54 UTC](https://discourse.nodered.org/t/event-on-change-of-digital-signal-status/23926/4 "2020-04-13T22:54:39Z")

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