# What is (single controller or agents) and (controller + unlimited agents) for EAM?

**URL:** <https://forum.inductiveautomation.com/t/what-is-single-controller-or-agents-and-controller-unlimited-agents-for-eam/29669>\
**Category:** Ignition\
**Tags:** ignition80\
**Created:** [November 5, 2019, 7:22am UTC](https://forum.inductiveautomation.com/t/what-is-single-controller-or-agents-and-controller-unlimited-agents-for-eam/29669 "2019-11-05T07:22:14Z")\
**Posts on this page:** 2\
**Page:** 1

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**Author:** ![srikantakumar.sahu](https://sea1.discourse-cdn.com/inductiveautomation/user_avatar/forum.inductiveautomation.com/srikantakumar.sahu/32/11364_2.png) [@srikantakumar.sahu](https://forum.inductiveautomation.com/u/srikantakumar.sahu)\
**Post date:** [November 5, 2019, 7:22am UTC](https://forum.inductiveautomation.com/t/what-is-single-controller-or-agents-and-controller-unlimited-agents-for-eam/29669/1 "2019-11-05T07:22:14Z")

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What is the difference between (single controller or agents) and (controller + unlimited agents)?  
For a plant to have one central ignition gateway and multiple client gateway in different geographic location. Which EAM module to purchase?

Does each client require a single EAM Module? Then what is the purpose of (controller + unlimited agents) EAM Module?

Please explain in details.

 ![image](https://us1.discourse-cdn.com/inductiveautomation/original/2X/5/537a8f6515f9cee8f6ace35edd52eeb0ab1cf8ba.png)  
 ![image](https://us1.discourse-cdn.com/inductiveautomation/original/2X/8/8edd31d5bcbcc3bf5b5581e4e484e3cfa4fedd98.png)

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**Author:** ![JordanCClark](https://sea1.discourse-cdn.com/inductiveautomation/user_avatar/forum.inductiveautomation.com/jordancclark/32/83362_2.png) [@JordanCClark](https://forum.inductiveautomation.com/u/JordanCClark)\
**Post date:** [November 5, 2019, 1:34pm UTC](https://forum.inductiveautomation.com/t/what-is-single-controller-or-agents-and-controller-unlimited-agents-for-eam/29669/2 "2019-11-05T13:34:06Z")

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Not much details. Simply put, it’s math.

Each gateway requires an EAM module to act as the controller or as an agent. At current pricing of $18900 USD, that would be a 14 unit break-even point.