DIN plugs - the analogue USB

"Many years ago most connections made between different pieces of audio equipment was by a standard known as DIN plugs and sockets. DIN stands for Deutsches Institut für Normung and it was a well designed piece of engineering with some sensible features. When putting a DIN plug into a DIN socket the first connection made was a large earth shield before the signal, very sensible. The socket also cleaned the signal pins when inserted and made a good tight connection. A different number of pins could be used and configured for both input and output using just one plug. It was in fact an analogue version of the USB cable we all use today. Vintage Sugden equipment used DIN connectors for years, it allowed us to connect equipment such as pre and power amplifiers with a single DIN plug. This could then supply both the signal and a power supply for the pre-amplifier. Tape recorders could have both record and playback." - Sugden Audio