Clocks may be surface, flush or double dial mounted and are available in 10", 12", 15" or 18" round and 12" square. Once each hour the master clock supervises the accuracy of the secondary clock system by issuing an eight second signal that will correct units up to 59 minutes and 55 seconds slow. Every twelve hours the master issues a 14 second supervisory signal to correct secondary clocks up to 11 hours, 59 minutes slow. The reference time for the hourly correction is the 59th minute and reference hours for the 12-hour correction are 6:00 AM and 6:00 PM. Flush mount clocks require a flush backbox. Each clock is supplied with a pair of Molex® connectors.