I did the WAV Trigger in my 1956 Williams Crossfire.
It was a lot of work.
I had to add a relay bank to interface with the 50 volt signals to each target.
I was very pleased with the results though I was never able to completely eliminate the ghost trips.

I set up my game to run either the bells that it came with or digital sound via the WAV-Trigger.
It is cool that you can choose your own sounds when you set it up.

That looks much simpler than adding sound to a machine that did not come with it.
This is the relay board I made to adapt a WAV.Trigger card work for 16 sounds in my Crossfire.

Relay pack (resized).jpg

No, the relays are 48v coil relays. The machine has 50 volt coils on the targets.

If you look close you will see I soldered 2 additional wires on each coil that runs back to each relay.
Each target has an EOS so the pulse is short.
Each target triggers an individual sound from the wav trigger board.
I also added the cowboy theme ( think: the good the bad and the ugly) when the coin drops to run for 90 seconds.

One of the relays is used to switch back to the original bells if I prefer. It is wired to a toggle inside the coin door. So it is either scoring bells or digital sound.