A system of circuit logic is described in which transistors, particularly diffused base transistors, are operated well out of saturation in order to make the most of their speed. Logical information is contained in the presence or absence of a current which can be switched or routed by the gates described. Also described is the application of this system of logic to certain specific computer problems, namely, a parallel adder with a carry propagation time of 40 mμsec over 6 stages, a shifting register capable of operating at 10 mc and a binary decoder with a maximum delay of 40 mμsec.