Sper Scientific 810045 Visual and Audible Continuous Alarm Timer Sper Scientific 810045 Visual and Audible Continuous Alarm Timer. Select either a bright flashing yellow LED visual alarm or an audible alarm. A memory recalls the last timer setting for reuse. Flashing yellow LED visual alarm or an audible alarm Count Up Channel: 0 Count Down Channel: 1 Range: 99 Hours 99 Minutes