# Notecard accepting external wired inputs like an external button

**URL:** <https://discuss.blues.com/t/notecard-accepting-external-wired-inputs-like-an-external-button/278>\
**Category:** Hardware\
**Created:** [May 28, 2021, 5:02pm UTC](https://discuss.blues.com/t/notecard-accepting-external-wired-inputs-like-an-external-button/278 "2021-05-28T17:02:08Z")\
**Posts on this page:** 1\
**Showing post:** 3

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**Author:** ![RobLauer](https://sea2.discourse-cdn.com/flex020/user_avatar/discuss.blues.com/roblauer/32/1567_2.png) [@RobLauer](https://discuss.blues.com/u/RobLauer)\
**Post date:** [May 28, 2021, 5:53pm UTC](https://discuss.blues.com/t/notecard-accepting-external-wired-inputs-like-an-external-button/278/3 "2021-05-28T17:53:42Z")

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@eyang I might be leading you down a slightly incorrect path. The [card.aux API](https://dev.blues.io/reference/complete-api-reference/card-requests/#card-aux) is likely what you are looking for.

In the meantime please take a look at this thread with an example of `card.aux` and I’ll be back with some follow-ups:

> [@Setting a notecard serial number "sn" remotely](https://discuss.blues.com/t/setting-a-notecard-serial-number-sn-remotely/174/2):
>
> Hi @Pat, Yes, in fact you can use [environment variables](https://dev.blues.io/build/notecard-guides/understanding-environment-variables/) to set the “serial number” for a device. Use \_sn to override any previously-entered serial number. Use \_sn\_default to set it, but not override the value if set already on the Notecard. To access environment variables, look at the “Environment” tab when browsing device details:

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