SACA Programmable Controller Systems 1 (C-207) Certification Practice Exam

In a PLC configured for Active Low logic, an active input signal is represented by a low voltage level. This means that when the input reads a voltage close to 0 volts, it indicates that the corresponding condition or input is "active" or "true" within the control logic. The concept of Active Low relies on the logic where a low state (below a set threshold) signifies an active condition.

In this context, 0V DC is interpreted as an active signal, as it signifies that the input is turned "on." Conversely, higher voltage levels such as 5V DC, 12V DC, or 24V DC represent inactive states in an Active Low configuration, indicating that those conditions are not currently true, hence they do not signify activation of the input. Therefore, in this scenario, the logical and correct answer is indeed 0V DC as the active input signal.