Shorten signal duration (pulse)
The circuit can shorten the signal duration of switches, levers etc.. The circuit does not need a piston (the piston that can be seen is not absolutely necessary) and is easy to rebuild. Application is e.g. to be able to process the signal from the daylight sensor.
Industrial furnace extension
As soon as there is only max 64 coal left in the oven, a light starts flashing and you know that you should refill.
Defense in disguise
The principle works with a bug: If a block is in front of a caster, it is penetrated by e.g. an arrow. This way an opponent can be attacked unnoticed, e.g. in a prepared canyon.