The scheme is a monopole using a mixture of overhead line and submarine cable for the 200 kV high voltage conductor, and sea return for the neutral current.

When originally completed in 1968 by English Electric, the scheme comprised two converter stations, at San Dalmazio in Tuscany on the Italian mainland, which was situated close to a production area and offered a connection to two 220 kV lines, and Codrongianos on Sardinia.

Each 6-pulse converter bridge consisted of 6 main mercury-arc valves plus a 7th for high-speed bypass operations.

Although the converter stations are inherently capable of operating in either direction of power transmission, advantage was taken of the unidirectional power-flow requirement to economise on the design of the sea electrodes.

However, the anode electrode on Sardinia required a more sophisticated design using platinum-coated titanium pipe, subdivided into 30 sub-electrodes, in order to prevent corrosion.

It is planned to replace the existing scheme with a bipolar system with a transmission rate of 400 MW called SACOI 3.

While the overhead lines can be used without modification, the underground and underwater cables have to be replaced for the higher transmission rate.