I am not sure what you want to do. What is the external bell ringer? Is it a phone?

Any response to this? He clarified the request.

If you're looking to connect it as a ringer to an overhead PA, you can get the Algo 8301 or SNOM PA1, connect them to your amp and register them as "other phones" in RingCentral. You'll have to pay for a digital line if you need this, so keep that in mind. Once that's done, though, you can then have the 8301 or PA1 ring in tandem with your phones and they will simultaneously ring overhead as well.

If you're just looking to connect to a physical Poly phone, you can get the Algo 2507 and either an Algo 8180 or 8186. This does not require an additional line/seat, you basically just connect the 2507 to the headset jack of your Poly phone and the other end of the 2507 to the relay input of the 8180 or 8186 via their terminal blocks. Then log into either your 8180 or 8186 and navigate to the Input/Output section and change the relay input mode to the 2507 ring detector.

I found the instructions on Algo's website for getting this to work. We are a Restaurant company and use the Shared Lines feature so this is how we got it to work using the 8180 G2.

https://www.algosolutions.com/wp-content/uploads/2021/07/2506-Install-Guide.pdf