# 1 NFC tag with multiple devices? **URL:** \ **Category:** Factual Questions\ **Created:** [February 19, 2016, 12:34am UTC](https://boards.straightdope.com/t/1-nfc-tag-with-multiple-devices/746504 "2016-02-19T00:34:18Z")\ **Posts on this page:** 9\ **Page:** 1
**Author:** ![birdbrain](https://avatars.discourse-cdn.com/v4/letter/b/dfb087/32.png) [@birdbrain](https://boards.straightdope.com/u/birdbrain)\ **Post date:** [February 19, 2016, 12:34am UTC](https://boards.straightdope.com/t/1-nfc-tag-with-multiple-devices/746504/1 "2016-02-19T00:34:18Z")
I have never used NFC tags before but will have some arriving soon. I have searched for the answer to this but can’t seem to find a clear answer. Can one NFC tag be programmed to work with more than one device or does it only work with one? What I am hoping to do is use one tag to serve as part of a time and attendance system. Eventually I plan to get a biometric time clock but this idea just came to me and I’m wondering if it would work. Currently I have employees with no direct supervision logging their own hours and I’m fairly certain that there is more than a little time stealing going on. I was thinking that each employee could program their phone to send a text to my phone upon arriving to and leaving from work. I’d rather have one tag if possible to eliminate the possibility of just taking the tag home and clocking in and out from a remote location. Any thoughts or suggestions? ---
**Author:** ![GaryM](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/garym/32/241_2.png) [@GaryM](https://boards.straightdope.com/u/GaryM)\ **Post date:** [February 19, 2016, 1:11am UTC](https://boards.straightdope.com/t/1-nfc-tag-with-multiple-devices/746504/2 "2016-02-19T01:11:51Z")
I’m not an expert but have played with tags a little bit. The ones I’ve used are not programmed, but have an ID. You program the receiving device to perform a task when it recognizes that tag. I hope that helps. ---
**Author:** ![birdbrain](https://avatars.discourse-cdn.com/v4/letter/b/dfb087/32.png) [@birdbrain](https://boards.straightdope.com/u/birdbrain)\ **Post date:** [February 19, 2016, 1:51am UTC](https://boards.straightdope.com/t/1-nfc-tag-with-multiple-devices/746504/3 "2016-02-19T01:51:55Z")
Thanks Gary, I have a general understanding of how they work and what can be done with them. I just want to know if one tag can be used with several devices or if each device would require its own tag to carry out the action desired. ---
**Author:** ![Isilder](https://avatars.discourse-cdn.com/v4/letter/i/cc9497/32.png) [@Isilder](https://boards.straightdope.com/u/Isilder)\ **Post date:** [February 19, 2016, 2:09am UTC](https://boards.straightdope.com/t/1-nfc-tag-with-multiple-devices/746504/4 "2016-02-19T02:09:07Z")
One tag can work with many NFC device… Its up to your app to detect the NFC tag’s ID … However it might be a copied ID, surely someone is selling an NFC tag that can be 100% written… so its 100% a copy… However changing the data at key times will put the fear of being caught into the employees, they won’t try to copy the data or they will be caught out doing that ! ---
**Author:** ![birdbrain](https://avatars.discourse-cdn.com/v4/letter/b/dfb087/32.png) [@birdbrain](https://boards.straightdope.com/u/birdbrain)\ **Post date:** [February 19, 2016, 3:08am UTC](https://boards.straightdope.com/t/1-nfc-tag-with-multiple-devices/746504/5 "2016-02-19T03:08:21Z")
Thank you Islider, that is very helpful. ---
**Author:** ![gotpasswords](https://avatars.discourse-cdn.com/v4/letter/g/c57346/32.png) [@gotpasswords](https://boards.straightdope.com/u/gotpasswords)\ **Post date:** [February 19, 2016, 7:05am UTC](https://boards.straightdope.com/t/1-nfc-tag-with-multiple-devices/746504/6 "2016-02-19T07:05:42Z")
We use contactless badges where I work, and one tag or badge can be read by any of thousands of readers in the global enterprise. In theory, I could request access to an office in London and have that privilege added to my badge through the centralized access management system. At its heart, the tag is just an electronically readable number. What you do when that number is read by a device in your system is up to you. Not sure what good it will do to have employees’ phones send you a text. If you’re thinking of doing anything involving employees’ personal phones, be very careful as you could run afoul of privacy laws. ---
**Author:** ![UDS](https://avatars.discourse-cdn.com/v4/letter/u/ecae2f/32.png) [@UDS](https://boards.straightdope.com/u/UDS)\ **Post date:** [February 19, 2016, 7:17am UTC](https://boards.straightdope.com/t/1-nfc-tag-with-multiple-devices/746504/7 "2016-02-19T07:17:49Z")
> [@gotpasswords](#): > > . . . Not sure what good it will do to have employees’ phones send you a text. If you’re thinking of doing anything involving employees’ personal phones, be very careful as you could run afoul of privacy laws. Or of the reluctance of employees to provide equipment for company purposes at their own expense. You want me to carry a phone that sends you an automated text when I enter or leave the building? You provide the phone, so. And pay the telco bills. ---
**Author:** ![Tim\_T-Bonham.net](https://avatars.discourse-cdn.com/v4/letter/t/46a35a/32.png) [@Tim\_T-Bonham.net](https://boards.straightdope.com/u/Tim_T-Bonham.net)\ **Post date:** [February 19, 2016, 7:39am UTC](https://boards.straightdope.com/t/1-nfc-tag-with-multiple-devices/746504/8 "2016-02-19T07:39:06Z")
> [@birdbrain](#): > > Any thoughts or suggestions? I suggest evaluating employees by the work they get done, not the hours they serve. ---
**Author:** ![bob\_2](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/bob_2/32/3341_2.png) [@bob\_2](https://boards.straightdope.com/u/bob_2)\ **Post date:** [February 19, 2016, 8:56am UTC](https://boards.straightdope.com/t/1-nfc-tag-with-multiple-devices/746504/9 "2016-02-19T08:56:17Z")
> [@t-bonham@scc.net](#): > > I suggest evaluating employees by the work they get done, not the hours they serve. I guess that there are a few jobs where actually being there is more important than the work done. Night security comes to mind. That said, as a one time manager, it was my experience that the guy who is never late and always works over, is almost never the most valuable member of the team. And yes - I think that you would have to provide the phones.