The Howler is an add-on to any 100-200 watt warning siren such as the Whelen 295SL Series. Works with most Siren Amplifiers. Includes two speakers for use with Howler amplifier only. �Works with any sweeping tone, plus Hi/Low and electronic mechanical tone generated by the primary siren. The Howler low-frequency tones are synchronous with your primary siren tones to penetrate high noise, high traffic situations. The Howler Siren Amplifier module uses the primary siren speaker output wires and divides the frequency down to one of three frequency bands via dip switch. Selections are 1/4 tone, 1/2 tone or a composite of 1/4 and 1/2 tones. Lower frequency reverberating tones are better able to penetrate other vehicles, alerting drivers to the presence of the oncoming emergency vehicle. Push on/push off button activates/ deactivates the siren, allowing radio transmission to the vehicle without waiting for the unit to time out. Built-in timer limits overexposure time to operator. Operators are advised to wear approved hearing protection. Two separate external cancel controls, standard. A positive or negative activation will cancel tone. Select tone duration and tone style via easy Scan-Lock™ feature and LED indicator. (selection of 8 different tone durations: 8-60 seconds maximum)