Transistor circuits for a digital differential analyser

The digital differential analyser is a type of computer combining digital accuracy with analogue speed and flexibility. Where maximum flexibility is required, the organization of a machine of reasonable size demands many switching elements, and it seems doubtful whether thermionic valves would be sufficiently reliable. Transistors, however, offer sufficient reliability to make a design feasible, and the paper describes several practical circuits which are used in digital differential analysers.