The OR gate is based on the activation of molecule A, and thus pass electron / photon to molecule Cs excited state orbitals (C*). The electron from molecule A inter system crosses to C* via the excited state orbitals of B, eventually utilised as a signal in the C*  emission. The OR gate uses two inputs of light (photons) to molecule A in two separate electron transfer chains, both of which are capable of transferring to C* and thus producing the output of an OR gate. Therefore, if either electron transfer chain is activated, molecule Cs excitation produces a valid/ output emission.