Voice Projection Wiring Scheme

I think I have the connections on the circuit board from the 

"Annunciator 2 in 1 5 tone / 3 tone electronic siren with mic." that I got from eBay figured out. I tested the buttons with my Multimeter to see which connection points on the board would give me a continuity reading when each button was pressed. One thing puzzles me a little is that they appear to be momentary buttons but yet when I watched videos on YouTube showing how the unit worked they appeared to be latching buttons, perhaps a pulse from the button temporarily locks a connection somewhere and when the button is activated  again it breaks the connections, not sure about that, or how that will work with the wiring scheme I am thinking of trying out. It's going to be a little experimenting I guess but from just fiddling about with it I think it should work with the simple SPST Relay setup I have worked out in my diagram. Some of the other bits on the board will be relocated like the indicator LED and Mic.