A modular family was born
It was the late 1960s and AT&T was now on the scene. It ordered its engineers at Western Electric, its manufacturing arm, to focus their brilliant minds on the problem. The team, including Edwin Hardesty and Charles Krumreich eventually came up with the solution: a rectangular moulded plastic connector that had multiple parallel conductors, plastic channels to isolate and insulate each circuit, insulation displacement contacts in the plug, and springy wire contacts in the socket. A later design would replace the spring wire contacts in the socket with fixed blades.
Focusing on insulation displacement meant that field technicians could now mass terminate the connector with a simple crimp tool. The connectors were also easier to manufacture in the huge numbers required for a system-wide conversion. Moulding the plug body also meant that strain relief could be integrated into the plug, in the form of a flexible bar that would be crimped down onto the cord jacket after the electrical connections were made.
The design would be modified yet again, returning to spring wire contacts in the socket and replacing the original metal latch that locked the plug into the socket with a moulded plastic latch. But the basic design of the modular plug was now determined and ready for the future. The Trimline phone, where the handset now contained the dial or keypad, was one of the first phones to use the new connectors and throughout the 1970s, a decade of both cultural change and technological innovation, phone companies across the country retrofitted millions of existing phones.
In the 1980s the powerful AT&T monopoly began to break up and the new modular connectors now played an important role in democratising the entire phone system. For the first time customers could go into a store and buy whatever colour or style of phone they wanted, rather than leasing as before. One housewife went out and bought a new phone while her husband was at work. When he arrived home she had managed to rewire the new RJ11 connector into the wall using a special DIY kit promoted by AT&T.
Intuitive design, easy extensibility to more or fewer conductors, and the saturation of the market thanks to a large installed customer base all led to the modular connector being accepted across a wide range of industries. In 1976 the Federal Communications Commission mandated that phone system connections be standardised for interoperability so that customers could finally connect their own equipment to the telephone network.
The mandate termed these specifications registration interfaces, and the modular connectors became known as registered jacks, or RJ for short. The RJ11 became the connector for plugging a telephone into the wall and the handset into the telephone, while the RJ14 was designed for connecting multiple lines leading to a single phone unit. Crucially, an eight-conductor modular connector eventually became the standard for Ethernet connections. This was the RJ45. Its original 8P2C modular connectors were later modified into an 8P8C configuration with an additional tab or latch to ensure correct orientation in the newly arriving ethernet local area network (LAN) revolution.