From 2007.igem.org

We try to methodologically obey a 3S Principle, that is, simplicity, straightforwardness and stupidity. Simplicity means that the device we designed will not interfere with the basic function of a host cell. To let the devices be straightforward means that we expect one device to fulfill one and only one specific function. And stupidity means that we can use them freely and will not have to think much about the genotype of the host strain.

The figure above shows the basic structure of our input device. It functions to convert chemical signals to the PopS (the flow of RNA Polymerase molecules along DNA) signals of CRP and CI, which are actually the wires of our system.