Can I hook up an external speaker to a 4424D+??

[gordo78]

We have Avaya 4424D+ phones all over the building and in the warehouse. We use the intercom feature, but the volume is not loud enough to be heard across the warehouse floor. We want to add a self powered speaker to the one phone on the ware house floor. A LOUD speaker. I have 120v available to hang it on the wall and to power it if I can somehow get a low level audio signal out of the phone.

Similar to the speakers at car dealerships outside where everyone can hear for 200' around.

Can I do this? I see a headphone jack on the bottom of the phone, but it is a four pin RJ25 style telephone jack. There is also a jack on the side that has two rectangular holes about .75" apart. and the only other jack is an 8pin RJ45 phone jack labeled ADJ.