Signatrol Model 30 Flashers are standard duty On-Off flasher units with variable speed and customizable cams. The standard unit is furnished with 50% cams, (single notch) so the "On" and "Off" periods are of equal length. The motor speed adjustment allows the overall cycle to be varied from one revolution of the cam shaft in two seconds (30 flashes per min) to one revolution in four seconds (15 flashes per min).