Tap the speaker feed and amplify it, that's all there is.


Another way would be to create an analog extension with the 4025 number, which requires a new number for the 4025. Then you can put a button with the analog number on the 4025 and use the analog port to drive a Viking PA2A. (Hey, I didn't say it would be cheaper!)


When I was young, I was Liberal. As I aged and wised up, I became Conservative. Now that I'm old, I have settled on Curmudgeon.