The black gear motor is the clock's timebase. It runs synchronously with the 60 hz line frequency, and is geared to 12 rpm. The four leaf switches on cams trigger in sequence every 5 seconds, to momentarily blank the display, enable the roll-over between the stepper relays, advance the 5-second relay, and finally, re-enable the display. The small relay to the motor's right is latched in momentarily by one of the leaf switches and the 5-second contacts to enable roll-over when the 5-second digit is rolling from 5 to 0.(Nobody (NOBODY))