my customer bought an xblue from amazon. they didnt know it didnt have a paging port. xblue tells me i can use a co line port with our existing bogen amp if i give it 24vdc in parallel. does the transformer go in ahead of the amp or behind the amp. thanks, dave.

No, no, NO. You do not want to put 24 VDC in parallel between the CO port and the paging input or you will cook the input of the paging equipment. If you want to do it right, invest in a Viking PI-1A adapter, or similar:

TAKE A LOOK HERE.

I've done a bunch of these, I have some spare Valcom units where you plug in the unused co line connection and use two screw terminals to go out to the Bogen input. One modular plug in, two screw downs and it works.

Thanks, Bracha