# Modbus communication: Wiring diagram for conversion of RS-485 2 wire to 4 wire

**URL:** <https://forumautomation.com/t/modbus-communication-wiring-diagram-for-conversion-of-rs-485-2-wire-to-4-wire/444>\
**Category:** Industrial Automation\
**Created:** [June 11, 2015, 5:36pm UTC](https://forumautomation.com/t/modbus-communication-wiring-diagram-for-conversion-of-rs-485-2-wire-to-4-wire/444 "2015-06-11T17:36:06Z")\
**Posts on this page:** 4\
**Page:** 1

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**Author:** ![instrumen](https://forumautomation.com/letter_avatar_proxy/v4/letter/i/65b543/32.png) [@instrumen](https://forumautomation.com/u/instrumen)\
**Post date:** [June 11, 2015, 5:36pm UTC](https://forumautomation.com/t/modbus-communication-wiring-diagram-for-conversion-of-rs-485-2-wire-to-4-wire/444/1 "2015-06-11T17:36:08Z")

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Modbus communication: Wiring diagram for conversion of RS-485 2 wire to 4 wire.

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**Author:** ![Zohaib\_Jahan](https://forumautomation.com/user_avatar/forumautomation.com/zohaib_jahan/32/496_2.png) [@Zohaib\_Jahan](https://forumautomation.com/u/Zohaib_Jahan)\
**Post date:** [October 24, 2016, 3:16pm UTC](https://forumautomation.com/t/modbus-communication-wiring-diagram-for-conversion-of-rs-485-2-wire-to-4-wire/444/2 "2016-10-24T15:16:11Z")

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I am trying to connect Floboss 107 to CentumVP (ALR121) but no success. (Wiring Diagram attached)

Can anybody help me?

 ![](https://cdn.forumautomation.com/original/1X/1a52b22710366debc0047fe08f0c7e818dc054ee.png)

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**Author:** ![carl\_e](https://forumautomation.com/letter_avatar_proxy/v4/letter/c/94ad74/32.png) [@carl\_e](https://forumautomation.com/u/carl_e)\
**Post date:** [November 18, 2016, 5:48am UTC](https://forumautomation.com/t/modbus-communication-wiring-diagram-for-conversion-of-rs-485-2-wire-to-4-wire/444/3 "2016-11-18T05:48:39Z")

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Positive to Positive: TX+/RX+ connects to A Negative to Negative: Tx-/Rx- connects to B

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**Author:** ![VIPIN\_KUMAR](https://forumautomation.com/letter_avatar_proxy/v4/letter/v/dbc845/32.png) [@VIPIN\_KUMAR](https://forumautomation.com/u/VIPIN_KUMAR)\
**Post date:** [June 14, 2018, 11:07pm UTC](https://forumautomation.com/t/modbus-communication-wiring-diagram-for-conversion-of-rs-485-2-wire-to-4-wire/444/4 "2018-06-14T23:07:23Z")

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This connection was working.