ACA penetrator 15

The Penetrator-15 (also known as the P-15) was introduced in 1981 and is nearly identical to its older brother, but is instead powered by a dual-sided Doerr (later Baldor) 15 hp AC motor, in either single or 3 ph. Other than motor horsepower, the P-15 is identical to the P-10, using the same core and body. The P-15 was available in both 8-port single-tone and 9/12-port dual-tone, and boasted a rating of 127 dB at 100 ft. The P-15 is most commonly found with the 8-port single-tone rotor, as the motor is much more capable of handling it and its higher performance made single tone a more attractive option.

A three-signal P-15 was available, which utilizes a solenoid-operated damper inside of the cylindrical intake, which would allow the siren to create pulse signals. The solenoid mechanism is housed in a rounded cover on the side of the intake. There was also a two-signal model that used a valve held closed by a spring. The valve would be forced open by the intake of air when the siren began operating, and when the siren shuts off, the spring overpowers the airflow and forces the valve back closed making the winddown much less audible. This was likely meant for urban use, silencing the siren quickly without using a brake or solenoid. It may have also been used as a weatherproofing measure. Three-signal units are very uncommon, with most active surviving units being in the Memphis, TN area, though none of them use their dampers.