# RS485 TCI Full Duplex
**URL:** https://forum.universal-robots.com/t/rs485-tci-full-duplex/6549
**Category:** Robot Communication
**Created:** [March 3, 2020, 1:35pm UTC](https://forum.universal-robots.com/t/rs485-tci-full-duplex/6549 "2020-03-03T13:35:00Z")
**Posts on this page:** 3
**Page:** 1
### Author:  [@jorge](https://forum.universal-robots.com/u/jorge)
#### Post date: [March 3, 2020, 1:35pm UTC](https://forum.universal-robots.com/t/rs485-tci-full-duplex/6549/1 "2020-03-03T13:35:00Z")
Hi,
I was wondering if anyone had experience connecting a full duplex rs485 device to the robot’s rs485 lines at wrist 3. The device I would like to interface with has two differential pairs, one for Rx and one for Tx making it a full duplex device. The robot, only has one pair for half duplex communication.
Can both Tx and Rx lines be connected to the same pair coming from the robot, I’ve read that this can be done with a 100 Ohm series resistor?
Any help would be greatly appreciated.
Thank you.
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### Author:  [@frederic.chaxel](https://forum.universal-robots.com/u/frederic.chaxel)
#### Post date: [March 4, 2020, 5:14am UTC](https://forum.universal-robots.com/t/rs485-tci-full-duplex/6549/2 "2020-03-04T05:14:48Z")
Hi,
Look at this, in particular Fig 3 and Fig 4 on page 4 : [https://www.analog.com/media/en/technical-documentation/application-notes/AN-960.pdf](https://www.analog.com/media/en/technical-documentation/application-notes/AN-960.pdf)
The terminaison resistor is explain on page 5.
If your device is using the line in a RS485 mode and not RS422 it will be OK (release the TX pair when not in use).
Bye.
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### Author:  [@jorge](https://forum.universal-robots.com/u/jorge)
#### Post date: [March 6, 2020, 3:17am UTC](https://forum.universal-robots.com/t/rs485-tci-full-duplex/6549/3 "2020-03-06T03:17:39Z")
Hi, thanks, I will review the info and let you know if it works
I’m also considering using the following:
> **[RS485 / RS422 Repeater / Extender / Converter (Industrial)](https://www.commfront.com/products/industrial-rs485-rs422-repeater-extender-converter)**
>
> The RPT-485\_422-2 is a multi-function, compact, rugged, industrial-grade RS485 repeater / extender, RS422 repeater / extender or RS485 to RS422 converter, which can be used to extend the RS485 or RS422 distance to up to 4000 ft (1.2km), or to...
> **[RS485 / RS422 Isolator / Repeater / Converter (Industrial)](https://www.commfront.com/products/industrial-rs485-rs422-isolator-repeater-converter)**
>
> The RPT-485\_422-4 is a rugged, industrial-grade, optically-isolated RS485 / RS422 isolator / repeater / converter, which can be used to isolate one group of RS485 / RS422 equipment from another, or to extend the RS485 or RS422 distance to up to 4000...