What type of signal does a digital input in a PLC accept?

A digital input in a PLC is designed to accept On/Off signals, which are also known as binary signals. These signals are characterized by their two distinct states: high (often representing a value of 1) and low (representing a value of 0). This binary nature is fundamental to digital systems, including programmable logic controllers, as they operate on binary logic to make decisions and control processes.

Digital inputs are typically used for sensing devices such as limit switches, push buttons, and relay contacts, which can provide a clear, defined signal representing either an active (On) or inactive (Off) condition. This simplicity ensures reliable and straightforward input processing within the PLC.

The other types of signals mentioned do not align with how digital inputs function. Variable voltage signals, for example, would typically be used in analog inputs, which can read a range of values instead of just two states. Similarly, continuous current signals imply varying levels of current over time, which does not fit the binary nature required for digital inputs. Impulse signals, while they can trigger reactions in a system, again do not provide the steady On/Off state that digital inputs are designed to interpret. Thus, the essential function of digital inputs relies entirely on recognizing binary signals, making