Siren amplifier for Motorola Syntor x9000

[Switchcars]

I have an 87 TX DPS SSP. It has the correct Motorola Syntor X9000. According to the file on the car, the original siren horn was a Federal Signal CP100, but looking behind the front bumper it doesn't look like that's what's currently installed.

My question is, what is the correct amplifier to use to connect the Motorola radio and control unit to the siren? Anyone know what setup they used?
To my knowledge there was not a separate siren control unit. The Motorola has buttons on it for both siren and P/A.