D-sub connectors were arguably the first and most widely established In/Out (I/O) interface connector and are so called because of their trapezoidal (vaguely “D” shaped) shell which provides mechanical protection, shielding and an inbuilt polarisation when mating male to female, whether cable-end or panel mounted. They’re still amazingly popular in control and instrumentation; audio, communications and I/O from Printed Circuit Board applications. The common Dsub connector has a steel shell, normally plated with nickel or tin although for anti-magnetic applications the base material may be brass and Stainless Steel shell versions are also built. The shell on the male dsub connectors is normally “dimpled” to create good electrical continuity with the mating female, thus ensuring EMI/RFI shielding if screened cables have been terminated to the shell. D-subminiature connectors are available in five standard shell sizes: 9, 15, 25, 37 and 50 way plus High Density versions with 15, 26, 44, 62 or 78 contacts. The dimensions of dsub connectors are generally in accordance with IEC 60807-2 (was DIN 41652), BS9523 F0018, MIL-C-24308 and satisfy IEC Recommendation 48B; because of this they are compatible and interchangeable across manufacturers.