bn-link short period repeat cycle intermittent timer, interval timer - day, night, or 24 hour operation bn-link controls any 125vac equipment requiring a device to be turned on and off at precise intervals. this timer has a wide range of uses including controlling hydroponic pumps, co2 injection, turning on and off exhaust fans, and more. it is easy to set and operate. cycle timing is adjustable for operation during the day, night, or 24 hours.