The circuit modules in the Collection show the rapid advances made in electronic packaging and miniaturisation. The earliest modules incorporate Magnetic Amplifiers reflecting the last application of this technology before the Transistor designs appeared using discrete devices. Again the earliest modules are hard wired but printed circuit boards became common in the 60’s. The early memory devices are core stote which survived because of the radiation resistance. Eventually integrated circuits appear of increasing complexity and high density packaging which combine with multi-layer printed circuit boards. He latest boards have a hollow air cooled core. Mother Boards arrived quite late and it was quite common to have a hand wired backplane through products in the late 70’s.