What happens when two XIC instructions are placed in parallel on a rung?

What happens when two XIC instructions are placed in parallel on a rung?

• A. Energizes if either is closed
• B. Energizes if both closed
• C. De-energizes when any is open
• D. Never energizes

Answer: (A)

In ladder logic, placing two XIC (Examine If Closed) contacts in parallel creates an OR-style path. Each XIC is true when its input is on (closed). With parallel paths, if either input is on, there’s a complete path from the power rail to the output coil, so the coil energizes. If at least one input is on, the rung fires; if both are off, there’s no complete path and the rung stays de-energized. This is why two XICs in parallel energize the output when either input is on. If they were in series, you’d need both inputs on to energize (AND behavior).

In ladder logic, placing two XIC (Examine If Closed) contacts in parallel creates an OR-style path. Each XIC is true when its input is on (closed). With parallel paths, if either input is on, there’s a complete path from the power rail to the output coil, so the coil energizes. If at least one input is on, the rung fires; if both are off, there’s no complete path and the rung stays de-energized. This is why two XICs in parallel energize the output when either input is on. If they were in series, you’d need both inputs on to energize (AND behavior).