# Using RS485 extension card as Master

**URL:** <https://forum.sierrawireless.com/t/using-rs485-extension-card-as-master/6603>\
**Category:** Legacy FX/FXT series\
**Created:** [July 23, 2013, 2:09pm UTC](https://forum.sierrawireless.com/t/using-rs485-extension-card-as-master/6603 "2013-07-23T14:09:49Z")\
**Posts on this page:** 2\
**Page:** 1

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**Author:** ![dharold](https://avatars.discourse-cdn.com/v4/letter/d/c2a13f/32.png) [@dharold](https://forum.sierrawireless.com/u/dharold)\
**Post date:** [July 23, 2013, 2:09pm UTC](https://forum.sierrawireless.com/t/using-rs485-extension-card-as-master/6603/1 "2013-07-23T14:09:49Z")

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Sorry guys, I am not a true hardware guy and want to connect my FXT009 to a sensor input using the RS485 extension card. The sensor input works as a slave in a master-slave configuration where both are half duplex. My limited research tells me that normally the master provides the bias for the lines. I find nothing in the FXT user guide that lets me know if the extension card will work in this manner. Can you tell me if this is possible?

Thanks,  
Don

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**Author:** ![gmalpart](https://avatars.discourse-cdn.com/v4/letter/g/cab0a1/32.png) [@gmalpart](https://forum.sierrawireless.com/u/gmalpart)\
**Post date:** [July 24, 2013, 12:26pm UTC](https://forum.sierrawireless.com/t/using-rs485-extension-card-as-master/6603/2 "2013-07-24T12:26:22Z")

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Hi dharold,

Please contact your distributor to discuss your specific need, or alternatively you can contact me in private and we shall look into your requirements.

Regards,