Mechanical trading is the same as "rulebased trading" is the same as "systematic trading" is the same as "algorithmic trading". Algorithmic trading and automated trading is not same thing. This is a big misconcetion, I see a lot of people wrongly belive that algorithmic trading got to be automatic. I've seen quant shops/hedgefunds/cta's that are semi-automated. Only an part of the process is automated and the order execution part is manual.