Federal Signal PA300 electronic siren - circuit producing sound

[Tallie]

I recently purchased a Federal Signal PA300 electronic siren "AS IS"(schematic here: http://www.simonthenerd.com/files/policesiren/PA300.pdf). After locating the pin-out, I wired it up to my power supply... and something in the circuit is producing the siren sounds... what is it? Is this normal? No speaker hooked up.

[amyk]

I see at least one transformer in the circuit... and they can produce sound like a speaker, although with far less efficiency.

[Tallie]

I see at least one transformer in the circuit... and they can produce sound like a speaker, although with far less efficiency.

Thanks. Yes. It appears to be the driver transformer. I put a probe on it and it's putting out 1.2Khz. I guess this is normal...