1) Belt are all connected per green and red wire, green wire going to input of an aritmetic combinator, red connected to output of the combinator
2) Constant combinator connected per red wire to the output of the artimetic combinator output
(3 red wire to powerpole was only for testing and seeing the signal going out and is not needed)
![Image](https://forums.factorio.com/images/ext/faefb775f47053025c5dec7c25835b48.png)
Settign of artimetic combinator
![Image](https://forums.factorio.com/images/ext/a15f3c0488004852920f4becce027e8c.png)
it outputs the amount of items which arent in this case "Iron Plates" so it will emit a red signal if a wrong item is on the belt
Setting of the Static combinator:
Sending a Dummy RED Signal with the Value 1 cause we cant ask for 0 signals in conditions
![Image](https://forums.factorio.com/images/ext/d33eca0f1c2c481d55ce267d96269baa.png)
Settings of the Belts:
![Image](https://forums.factorio.com/images/ext/6afb1e4af9e36d399acfb2522b30626b.png)
they read the output and on same time only work if RED Signal is 1 (the dummy value from the static combinator, could be any value which is set on the static combinator, dont need to be one)
Have fun with this build could be handy in some spots
![Wink ;-)](./images/smilies/icon_e_wink.gif)
Greetings Ralle