Is there a reverse function on chippers or shredders?

Most electric quiet shredders, petrol shredders and professional models are fitted with a reverse function, which is very useful and enables the machine to deal with jammed material. 

 

Most electric impact shredders do not have this function, as their cutting system relies on rotating blades, as opposed to quiet electric shredders which have devices like cogs to pull material through and can be reversed to push it back.