pogran@CCQ.BBN.COM (Ken Pogran) (06/17/88)
(Say, don't we have a "components" mailing list or something? This hardly seems like something for TCP-IP. Oh, well.) I thought a bit of history might be interesting: The "D-series" connectors made their debut in the 1950s to interconnect military electronics "modules", which at the time were assemblies in metal boxes that plugged into "pans" and "trays". Interestingly, they were NOT designed for cable applications and they were NOT designed to support weight: the modules in their little boxes were supported mechanically by the pans and trays. The connectors were, however, pretty rugged -- they were all MIL-SPEC varieties. By the way, to give an idea of the size and scale of things at the time, they were referred to in 1960s connector literature as "D-subminiature" connectors. The Bell System began the large-scale use of these connectors on cables with the introduction of DataPhones (Bell's trademark for their modem service). Remember the rather ornate-looking light gray hard plastic shells? One advantage of the D-series connectors was the density of pins, and their use really took off -- especially for cable applications, precisely what they were NOT designed for! Manufacturers have tried a lot of ideas to cope with cables and their weight, with not a lot of success; the basic design of the connectors just isn't intended for it. And couple that with cost-reduction efforts (seen any MIL-SPEC versions of these connectors in products you've bought recently?) which have made many of the connectors even flimsier and you have a recipe for trouble. On the other hand, there's the overkill approach: The old, nearly-impossible-to-get $75 48-series round connector that BBN spec'ed a long, long time ago for the 1822 Distant Interface connector ... (since replaced by a 37-pin D connector, of course!) Ken Pogran