# Tags to read from PLCA or PLCB (topic change as old InTouch) **URL:** \ **Category:** Ignition\ **Created:** [February 19, 2026, 10:04am UTC](https://forum.inductiveautomation.com/t/tags-to-read-from-plca-or-plcb-topic-change-as-old-intouch/114060 "2026-02-19T10:04:55Z")\ **Posts on this page:** 2\ **Page:** 1
**Author:** ![mateusz.nawrocki](https://avatars.discourse-cdn.com/v4/letter/m/96bed5/32.png) [@mateusz.nawrocki](https://forum.inductiveautomation.com/u/mateusz.nawrocki)\ **Post date:** [February 19, 2026, 10:04am UTC](https://forum.inductiveautomation.com/t/tags-to-read-from-plca-or-plcb-topic-change-as-old-intouch/114060/1 "2026-02-19T10:04:55Z")
Hi, I’m trying to replicate old InTouch behaviour using topic change for tags depending on which PLC is connected. I have two PLCs PLC\_A and PLC\_B. I wrote script with rolling counters between SCADA - PLCs which identify which PLC is a master and write other PLC\_A or PLC\_B to string tag called Topic. Tags are exactly the same in both PLCs so I was thinking about creating generic tags in Ignition which can read from PLC\_A or B thanks to changed topic. Is it possible to not address tags directly but to use my tag “topic” in a path so the tag will address to correct PLC? Thanks in advance. ---
**Author:** ![Greyship](https://avatars.discourse-cdn.com/v4/letter/g/898d66/32.png) [@Greyship](https://forum.inductiveautomation.com/u/Greyship)\ **Post date:** [February 19, 2026, 1:13pm UTC](https://forum.inductiveautomation.com/t/tags-to-read-from-plca-or-plcb-topic-change-as-old-intouch/114060/2 "2026-02-19T13:13:19Z")
Is this an Ethernet device? You could change the physical host name in the configuration through a scripting call: [system.device.setDeviceHostname | Ignition User Manual](https://docs.inductiveautomation.com/docs/8.3/appendix/scripting-functions/system-device/system-device-setDeviceHostname) I’ve used this to switch between an Emulator and a physical PLC that have identical tags.