Twist-on wire connector

They are widely used in North America and several European countries in residential, commercial and industrial building power wiring, but have been banned in some other jurisdictions.

While their exterior covering is typically made from insulating plastic, their means of connection is a tapered coiled metal insert, which threads onto the wires and holds them securely.

Another specialized connector version has a permanently attached wire pigtail protruding from the top of the insulated cap.

After settling in the Toronto area, he was employed as an electrician contractor for Ontario Hydro, converting gas-lit homes to electrical incandescent lighting.

Typically, a mechanic installed the insulated wires; then an electrician cleaned the exposed conductors, twisted them together, and dipped them into a pot of molten solder.

Seeking a safer, more efficient connection method, Marr, working in his home workshop, developed the first pressure-type wire connector.

The outer insulating tubular enclosure is then threaded on to the metallic cap and the job is completed.A connector more closely resembling the present-day twist-on type was patented in Canada by Marr in 1931, and in the US in 1933.

This table shows the de facto standard color coding various manufacturers use[citation needed] to indicate the range of sizes of conductors that may be joined with twist-on wire connectors.