Posted on 05/23/2014 10:38:35 AM PDT by null and void
Ubiquitous modular jack and plug connectors. Illustration courtesy of Bill Simon.
The invention of the modular jack and plug by Edwin Charles Hardesty, Charles Krumreiich, et al of Western Electric is, I believe, one of the most important moments in connector history.
To set the stage: before 1975 in America, the telephone company owned all of the phones and leased them to customers. The phones were designed to last about 40 years, and could withstand lots of abuse. But, by leasing the phones, the operating company was responsible for servicing its equipment. In this case, the service man needed to come to your home any time the phone was damaged and repair it. They also received a call whenever the customer wanted to move the phone to another room.
The phone company did an analysis of repair costs and found that, by far the largest cost failure mechanism was a damaged cord that needed replacement. The cords were vulnerable to being pulled, twisted, yanked, and otherwise abused by people and pets. ATT decided it needed a solution to enable the service man to repair damaged cords more quickly.
Note the simple stamped contact in the cross section view that pierces the foil conductor. Illustration courtesy of Bill Simon.
The outcome of that analysis was the need for a quick disconnect so that the cord could be quickly removed and replaced.
The invention itself was brilliant for a number of reasons, including:
Great idea, but how to implement this with over 200 million phones across the country?
The invention of the modular jack and plug is one of the most important in connector history, as it gave rise to 8-wire Ethernet connector systems today. Illustration courtesy of Bill Simon.
ATT decided to retrofit existing phones in the field rather than try to switch out so many phones of different vintages, colors, etc. This was a massive effort. The phone handset has four wires from the jack to the speaker and microphone. These wires were different lengths, but did have a common ring style contact that fit screws at the microphone and speaker. Western Electric contracted with Berg Electronics, recently acquired by DuPont, to make these assemblies at the rate of over 100 million per year. Berg built dedicated high speed cable assembly machines that pulled each wire to the right length and crimped a spade terminal on one end, and a splice on the other. The splice connected to about a half-inch of gold plated wire that became the spring half of the connector inside the jack. These machines were replicated so they could run at Berg and at Western Electric. They ran for about eight years full out while the ATT service staff went to every house in the country and retrofitted their phones.
When the installer arrived at your house, they replaced wall plates, took off the phone housing and replaced the hard wired cords with modular jacks, and did the same for the hand set. They pulled out the new cables and snapped it all together. It took only about 10 minutes and they were on to the next house.
After that, when the customer’s dog ate the cord, they called ATT. ATT said they could come next week, but if you wanted a phone immediately, stop by the ATT store and buy your new cord and install it yourself in minutes. Talk about how to turn a cost center into a profit center and still have a very happy customer!
As you know, this plug-and-jack concept has been subsequently used to connect virtually every phone to the network and the 8-wire versions have become the ubiquitous Ethernet connections to the world. Not a bad 38-year run for Mr. Hardesty and Mr. Krumreich!
RJ11 and RJ45 ...
right on!
RJ ...
I still have my old crimping tool just in case. BTT
DEC MMJ
The hardest part was wiring the Trimline phone that was on a party line. Tight quarters!
Sweet. Doggone but those old BNC network connectors were a pain.
ping
Ditto.
When my parents moved to another house (a duplex) in Philly after 50 years in the same row home with the same rotary phone that they rented from Bell of PA...my brother tells me that my father had the four phone wires from the 50 year old rented rotary phone and could not understand where to screw them into the modular jack that was in the new(er) house.
They ultimately did purchase their own phone and plugged it in, denying Bell of PA that monthly rental income...
I remember when I could start using them ... :-) ...
The interesting thing about technology is that it’s all about people. We see all this “stuff” around us but every piece of it contains all kinds of human drama if you dig deep enough. The very best technology comes from engineers who have not only the technical bent but also the ability to empathize with the user. Good engineering is an act of philanthropy.
Mighty Modular Jack: new comic superhero
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