The LeadLag block is used to schedule a number of units on/off. The 'units' property should be set to a bundle variable that imports the list units the command from the *unit program*. The unit program must have three variables for each unit: -unit stage number used to determine start order - unit alarm status as true/false (anything not true is considered false) - variable used to command the unit; this variable must be set via 'setExternal' block in the unit program. This block's 'numOn' property is used to command all the units on or off. Each unit in alarm is commanded to off. Any remaining units are commanded on until we reach the desired number on (using unit num ordering).