Controlling multiple units by means of a higher-level control device

An apparatus comprising multiple units and a higher-level control device,

• wherein the control device stores a first module of instructions that, when executed by the
• control device, cause the control device
• to send reference values to the units, each of the reference values being individually
• assigned to one of the units,
• to send an initialization signal to the units, and
• to send first count signals and second count signals to the units, the first count signals and
• the second count signals being the same for all of the units;
• and
• wherein each of the units has a memory and a counter and stores a second module of
• instructions that, when executed by the respective unit, cause the respective unit
• to receive and store the reference value individually assigned to the respective unit in the
• memory of the respective unit,
• to receive the initialization signal and to set a counter value of the counter of the respective
• unit to an initial value identical for all units upon receiving the initialization signal,
• to receive the first count signals and the second count signals, to increase the counter
• value of the counter of the respective unit by an identical fixed increment amount upon receiving
• each first count signal, and to decrease the counter value of the counter of the respective unit by
• an identical fixed decrement amount upon receiving each second count signal, and
• to determine a present target state of the respective unit by comparing the respective
• reference value stored in the memory of the respective unit with the present counter value of the
• counter of the respective unit.