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4 min

Beginner 03 — Two switches (OR)

beginnerfundamentalsorparallel
Beginner 03 — Two switches (OR) scenario preview

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Briefing

Two switches in parallel. The light turns on when SWITCH_1 OR SWITCH_2 is ON. Either one is enough. This is how you wire two start buttons — front-of-machine and back-of-machine — so an operator on either side can run the line. Parallel contacts read as OR.

Objectives

  • When SWITCH_1 is true, LIGHT turns on
  • When SWITCH_2 is true, LIGHT turns on
  • When both are false, LIGHT stays off

Hints

  • Place two normally-open contacts in parallel — one above the other on a branch.
  • Energy can take either path through the rung; either contact closing energises the coil.

I/O Table

Inputs

SWITCH_1

First switch (NO)

BOOL · %I0.0

SWITCH_2

Second switch (NO)

BOOL · %I0.1

Outputs

LIGHT

Indicator lamp

BOOL · %Q0.0

Your program will be tested against:

All test cases run automatically when you submit. Assertions are hidden until you pass.

  1. #1SWITCH_2 only → LIGHT on

    Either switch closed lights the lamp

  2. #2SWITCH_1 only → LIGHT on

    Either switch closed lights the lamp

  3. #3Both off → LIGHT off

    Both switches open keeps the light off

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