RS-232 Merger/Repeater Recommendations?

Merging RS232 basically can't be done reliably, as the merger would have to store-and-forward the commands from each device if they ever sent any data at the same time, and unfortunately there is no defined way for the merger to know when the command from Source A is finished so can send the stored commands coming from Source B.
- If they ever get interleaved, neither command will execute!

I recommend using an AV/Serial Interface station for the additional device. These are available for both Classic Unison and Unison Paradigm.

The AV/Serial Interface station provides a set of 'virtual' faders, buttons and indicators that are controlled via defined RS232 commands, and you can assign the relevant Actions directly to these 'virtual' buttons/faders/indicators.

Merging RS232 basically can't be done reliably, as the merger would have to store-and-forward the commands from each device if they ever sent any data at the same time, and unfortunately there is no defined way for the merger to know when the command from Source A is finished so can send the stored commands coming from Source B.
- If they ever get interleaved, neither command will execute!

I recommend using an AV/Serial Interface station for the additional device. These are available for both Classic Unison and Unison Paradigm.

The AV/Serial Interface station provides a set of 'virtual' faders, buttons and indicators that are controlled via defined RS232 commands, and you can assign the relevant Actions directly to these 'virtual' buttons/faders/indicators.

There are serial port combiners out there that will allow the first device that "speaks" to take control of the data stream (although I have not personally tested any of these devices some of our technicians have had success in the past). The only problem that I would foresee occurring is that if two devices were sending data at the same exact time one device would not get processed- probably unlikely with the setup you describe.

As Richard mentioned it is a more solid solution to add a UH1AV station to the job. If you do this I would suggest having the AV system utilize the RS232 PSAP port and the shade controller would then utilize the UH1AV station. 

Is it possible to throw the shade control into the AV systems scope and just have a single RS-232 interface from Paradigm to the AV system?

Take care!

Thanks to both of you for the info.   I'll look into these items.

One question-

Does the AV Interface station allow for custom serial commands to be sent back out of it?

No, the UH1AV station has a fixed syntax structure for sending and receiving.

Here is a link to the quick guide if you are interested in the syntax of the UH1AV station:

http://www.etcconnect.com/docs/docs_downloads/manuals/Unison_Heritage_AVSerialInterface_QuickGuide_revB.pdf

Take care!