They adorn the ends of Cat5 network patch cables and the flat satin cables that come with all-in-one printers that we generally either toss in the scrap bin or throw away altogether. The blocky rectangular plugs, molded of clear plastic and holding gold-plated contacts, are known broadly as modular connectors. They and their socket counterparts have become ubiquitous components of the connected world over the last half-century or so, and unsurprisingly they had their start where so many other innovations began: from the need to manage the growth of the telephone network and reduce costs. Here’s how the modular connector got that way.

Service as a Service

For the first 80 years or so of the US telephone network, the Bell Company called all the shots. They owned absolutely every bit of equipment in the system – the wires on the poles, the switchgear in the central offices, microwave links, and even the phone sets in customer homes. They had complete control over every aspect of the delivery of their services, and used their monopoly to build an incredibly integrated and durable system.

But with great power comes great responsibility, or in the case of a complex technological system prone to breakdown no matter how robust it is, a great support burden. Customers were completely reliant on phone company technicians for everything. Want a phone moved to another room? That’s a service call. Dog chewed the cord between the set and the wall? Service call. Junior got the scissors and decided to clip the handset cord? Most definitely a service call. Some services were charged back to the customer, but even for phones built like a battleship with a design life of 40 years, wear and tear eventually add up.

Sinking ever more money into customer service calls, AT&T decided to look into ways to minimize costs in this area. With mountains of service tickets to provide raw data, they discovered that by far the most common calls were for broken cords between the base and the handset. That’s understandable; the handset cord is twisted and kinked, and despite ample strain reliefs at stress points, eventually the cord frays and breaks. Not only were there a lot of broken cord calls, but each one required a good chunk of the technician’s time to correct, as the phone had to be disassembled for the dodgy cord to be replaced.

To reduce the service burden, in the late 1960s AT&T turned the engineers at Western Electric, its manufacturing arm, on the problem. The team, including Edwin Hardesty and Charles Krumreich, looked at the specs. They knew they needed four conductors, and that the connector had to be easily and rapidly disconnected in the field. The connector would have to have strain relief built in, be easily manufactured, and be cheap. It was also desirable to have the handset connector be generally useful, in particular for replacing the cord between the phone and the …read more

Source:: Hackaday