Characterisation of the nature and scope of the intervention in a control system by the operator and by feedback from the system to be controlled. Here in accordance with DIN 19 237 a differentiation is made between six variants:
automatic mode:
Operating mode in which the control operates without intervention from the operator according to a program in a control sequence that is specifically started (automatic control).
semi-automatic mode:
Operating mode in which only part of the control or the program operates automatically without the intervention of the operator (semi-automatic control).
manual mode:
Operating mode in which the control system operates only as a result of the intervention of the operator as a function of any interlocks.
initial setting mode:
Operating mode in which actuators are controlled separately by the setter while bypassing any existing interlocks.
step setting mode:
Operating mode for sequential control in which the sequence chain can be set to any step by the operator.
inching mode:
Operating mode for sequential control in which switching the sequence chain to the next step is dependent on the intervention of the operator using asignal generator provided only once for the entire sequence chain for this purpose.
As rule the health and safety regulations require that the selector switch with which these operating modes are set has a lock to prevent misuse by the operator.